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The distribution and abundance of the root weevil : Hylobius warreni Wood in relation to Lodgepole pine… Cerezke, Herbert Frederick 1968

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THE DISTRIBUTION AND ABUNDANCE OF THE ROOT WEEVIL, HYLOBIUS WARRENI WOOD IN RELATION TO LODGEPOLE PINE STAND CONDITIONS IN ALBERTA by HERBERT FREDERICK CEREZKE Sc. (1959) , M.Sc. (1962) , University of Alberta A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of FORESTRY We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1968 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I a g r e e t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s j s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f C^To^^dk^ The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date ABSTRACT The d i s t r i b u t i o n , p o p u l a t i o n ecology, behavior and host i n t e r a c t i o n s of the root w e e v i l , Hylobius warreni Wood were i n v e s t i g a t e d i n lodgepole pine f o r e s t s i n A l b e r t a . Highest incidence of the w e e v i l occurs i n the.Lower F o o t h i l l s S e c t i o n cf the B o r e a l Forest Region, between 2 ,500 and 4 ,000 f e e t i n e l e v a t i o n . I n even-aged f o r e s t s w e e v i l numbers are d i s t r i b u t e d according to stand maturity, stand d e n s i t y , t r e e s i z e and d u f f depth. I n t e r a c t i o n s between these v a r i a b l e s modify the p a t t e r n s of abundance i n d i f f e r e n t stands. A t t a c k incidence upon the host v a r i e s , being highest i n the c o l l a r zone and l e a s t on l a t e r a l r o o t s . As t r e e s i z e increases the r a t i o of w eevils on r o o t s tends to i n c r e a s e . During normal stand development i n i t i a l w e e v i l s on c o l l a r i n v a s i o n of weevils occurs at age 6 -10 years, and p e r s i s t s w i t h successive a t t a c k s throughout the l i f e of the stand. Weevil populations are h i g h l y aggregated i n mature stands; "k" values of the negative b i n o m i a l v a r i e d from 0.09 t° 0 . 6 8 , w h i l e Taylor's power law gave an aggregation index "b" value of 1 . 9 2 . Estimates of w e e v i l populations i n d i c a t e d t h a t low l e v e l s are c h a r a c t e r i s t i c of t h i s species and are maintained, mostly w i t h i n the range 200-1200 weevils per acre. Estimates of absolute numbers i n d i c a t e s i m i l a r l e v e l s of abundance occur i n young and o l d stands a l i k e , w h i l e p o p u l a t i o n i n t e n s i t y values increase w i t h stand maturity. The highest r a t e of increase of a t t a c k d e n s i t y per t r e e appears to occur during the ages of 30 -45 years. The s t r u c t u r e of w e e v i l populations was described and m o r t a l i t y f a c t o r s were i d e n t i f i e d and measured f o r l a r v a l , pupal and t e n e r a l stages. i i The main m o r t a l i t y f a c t o r o f these stages appeared to be from excess moisture i n the l a r v a l g a l l e r y and pupal c e l l . Only the f i r s t 3 l a r v a l i n s t a r s are d e f i n a b l e by head capsule width measurement. The feeding behavior of larvae v a r i e s w i t h i t s m a t u r i t y . I n the e a r l y i n s t a r s the feeding p a t t e r n r e l a t e s to bark t h i c k n e s s , but damage i s i n s i g n i f i c a n t . Damage of l a t e i n s t a r s may c o n s i s t o f d e c o r t i c a t e d g a l l e r y lengths up to 2h cm. L a r v a l and pupal h a b i t a t s are described to i n d i c a t e the s p e c i a l adaptations f o r s u r v i v a l . A d u l t s l i v e at l e a s t 3 years but l a y t h e i r eggs during the second and t h i r d summers of adulthood. Their seasonal peak o f a c t i v i t y occurs i n June and e a r l y J u l y . D i s p e r s i o n i n the f o r e s t tends to be random, commencing about 2 hours a f t e r sunset and when temperatures exceed 36 -^0 °F. Host trees are l o c a t e d p a r t l y by v i s i o n , the p a t t e r n of s e l e c t i o n being r e l a t e d to host s i z e . Maximum f e c u n d i t y per female per season may be 36 or more eggs, but i n the f i e l d the a c t u a l number may not exceed 1 2 . Q . Most eggs are deposited s i n g l y i n niches excavated by the female i n the r o o t - c o l l a r bark, and are subsequently covered over w i t h e x c r e t a . The egg r e q u i r e s a moist-environment maintained f o r up to k2 days f o r s u c c e s s f u l hatch. During stand development up to 100 percent of tre e s may s u s t a i n l a r v a l feeding damage accumulated to va r i o u s degrees of i n t e n s i t y . Young . t r e e s up to 30 years of age show l e s s r e s i s t a n c e to g i r d l i n g damage than o l d e r t r e e s , and reasons are given f o r t h i s . Estimates of mean height losses of 2 0 - 2 5-year o l d t r e e stems s u s t a i n i n g 50 percent g i r d l i n g were 11 .5 and 10-.9 percent over 2 - and 3-year periods r e s p e c t i v e l y . The t o t a l impact of the w e e v i l i n the stand as a whole appears to hasten s u c c e s s i o n a l changes i i i d u r ing stand development. A method o f r e g u l a t i o n of w e e v i l abundance i s p o s t u l a t e d and takes i n t o account the behavior of the female during o v i p o s i t i o n , host s e l e c t i o n , l a r v a l feeding h a b i t s , cumulative damage and host i n t e r a c t i o n s . O v e r a l l numerical r e s t r a i n t and s t a b i l i t y of numbers are considered to be .effected l a r g e l y through the inherent behavior of a d u l t s . S e v e r a l w e e v i l c o n t r o l measures are suggested through f o r e s t management. C l e a r c u t t i n g o f mature timber i n a l t e r n a t e s t r i p s reduced a w e e v i l p o p u l a t i o n by an estimated 67 percent, but some larvae developed to ad u l t s i n the cut stumps one and two years a f t e r t r e e removal. The e f f e c t on of cutting r e s u l t e d i n a concentration of weevils adjacent t r e e s along stand A p e r i p h e r i e s , 3 - 5 years a f t e r c u t t i n g . i v ACKNOWLEDGEMENTS I extend my s i n c e r e a p p r e c i a t i o n to Dr. K. Graham, f a c u l t y advisor at the U n i v e r s i t y of B r i t i s h Columbia f o r h i s guidance and v a l u a b l e c r i t i c i s m s during the p r e p a r a t i o n of t h i s t h e s i s , and to Drs. A . Kozak and G. G. E. Scudder, a l s o at the U n i v e r s i t y of B r i t i s h Columbia f o r t h e i r review of the manuscript. To my colleagues i n the Dept. of F i s h e r i e s and F o r e s t r y at Calgary, I am indepted p a r t i c u l a r l y t o : Dr. R. F. Shepherd who provided considerable encouragement and a s s i s t a n c e i n techniques of sampling and analyses, to Hr. L. S a f r a n y i k f o r h i s e n l i g h t e n i n g d i s c u s s i o n s and advice on s t a t i s t i c a l matters and to Dr. G. P. Thomas f o r h i s h e l p f u l a t t i t u d e . Permission to use departmental data f o r t h e s i s purposes was granted by Mr. W. A. Reeks, Entomology Program Coordinator i n Ottawa. I express thanks to s t a f f members of North Western Pulp and Power L t d . at Hint-on f o r p r o v i d i n g f i e l d experimental areas f o r work and to members of the A l b e r t a Forest S e r v i c e f o r p r o v i d i n g i n f o r m a t i o n on stand c o n d i t i o n s . The f o l l o w i n g persons were contacted f o r i n f o r m a t i o n on d i s t r i b u t i o n records; t h e i r a s s i s t a n c e i s hereby acknowledged. Dr. C. L. Massey, Rocky Mt. Forest and Range Expt. Stn., Albuquerque, New Mexico; Dr. R. P r i c e , , D i r e c t o r , Rocky Mt. Forest and Range Expt. Stn., F o r t C o l l i n s , Colorado; Miss Rosa E. Warner, U. S. N a t i o n a l Museum, Washington D.C.; Mr. D. G. F e l l i n , Inter-mountain Forest and Range Expt. Stn., Missoula, Montana; Mr. C. A. Wellner, Inter-mountain Forest and Range Expt. Stn., Ogden, Utah; Dr. W. F. Barr, Dept. of Entomology, U n i v e r s i t y of Idaho, Moscow, Idaho; Dr. M. H. Hatch, Burke Museum, U n i v e r s i t y of Washington, S e a t t l e , Washington; Dr. R. L. F u r n i s s , P a c i f i c Northwest Forest and Range Expt. Stn., P o r t l a n d , Oregon; V Mr. H. B. Leech, The Science Museum, C a l i f o r n i a Academy of Sciences., San F r a n c i s c o , C a l i f o r n i a and Dr. D. C. Schmiege, Northern Forest Expt. Stn., Juneau, A l a s k a . I am g r a t e f u l to Mr. J . Grant, Can. Dept. F i s h e r i e s and F o r e s t r y , Vernon, B. C. f o r granting'permission to use h i s w e e v i l d i s t r i b u t i o n data from B r i t i s h Columbia and the Yukon T e r r i t o r y . S p e c i a l thanks are due to Dr. Gertrud K l o s s , Sao Paulo, B r a z i l and to Dr. W. Ruhm, Hannover, Germany f o r t h e i r i d e n t i f i c a t i o n of nematode p a r a s i t e s . F i n a l l y , I would l i k e to thank- the many student and t e c h n i c a l s t a f f members who a s s i s t e d i n c o l l e c t i n g , a n a l y s i n g and i n p r e p a r i n g graphs f o r f i n a l p r e s e n t a t i o n of data, i n p a r t i c u l a r Mr. R. Gordey. v i TABLE OF CONTENTS Page ABSTRACT i ACKNOWLEDGEMENTS .'. i v TABLE OF CONTENTS v i LIST OF TABLES i x LIST OF FIGURES AND ILLUSTRATIONS x i i INTRODUCTION 1 1. H i s t o r i c a l Review 2 MATERIALS AND METHODS 5 1 . The Study In s e c t 5 1 . 1 . Taxonomy 5 • 1 . 2 . L i f e Stages and Habits 6 1 . 3 - Host Species and Geographical D i s t r i b u t i o n 7 2 . Studies of Hylobius 'Populations 8 2 . 1 . Study Areas 9 2 . 1 . 1 . D e s c r i p t i o n of Lower F o o t h i l l s S e c t i o n 11 2 . 2 . Design of P l o t s and Sampling Procedure 20 2 . 2 . 1 . P l o t s i n mature pine 20 2 . 2 . 2 . P l o t s i n regeneration pine 22 2 . 3 - Techniques of Po p u l a t i o n A n a l y s i s 23 2 . 3 . 1 - Treatment o f sample tr e e s 23 2 . 3 . 2 . Weevil numbers and p o p u l a t i o n s t r u c t u r e 23 2 . 3 . 3 . Weevil d i s t r i b u t i o n p a t t e r n s i n the f o r e s t and on the host 26 2 . 3 . 4 . Weevil a t t a c k p a t t e r n s 27 3 . Studies of the L i f e Stages of H. warreni 30 3 . 1 . L a r v a l Stage 30 3 . 2 . Pupal Stage 33 3 . 3 . M o r t a l i t y F a c t o r s of A l l Stages 33 3 . 4 . A d u l t and Egg Stages - 34 3 . 4 . 1 . C o l l e c t i n g methods, a d u l t numbers and sex r a t i o s 34 3 . 4 . 2 . D i s p e r s a l P a t t e r n s o f Adults 37 3 . 4 . 3 . Weevil r e p r o d u c t i o n 39 v i i Page 3.^ .^ -. Light and temperature response and orientation of adults 44 3 . ^ . 5 . Adult.-' feeding pattern 47 4. Studies of the Effects of Weevil Damage to Trees 47 4 . 1 . Anatomical Effects 48 1+.2. Growth Loss Effects 48 RESULTS 52 1. D i s t r i b u t i o n of Hylobius warreni 52 2 . General Characteristics of the Weevil Habitat 55 3 . Weevil Abundance, Their Change with Time and Attack Density . 6l 4. Relationship of Weevil Numbers with Stand Conditions 83 4 . 1 . Relationship With Tree Size 83 4 . 2 . Relationship with Tree Density 83 h.3. Relationship with Duff Depth 88 4 . 4 . Relationship with Clearcutting 97 4 . 5 . Relationship with Stand Maturity 100 5. Patterns of Weevil Attack 101 5 - 1 - I n i t i a l Weevil Invasion into Regeneration Pine 101 5 . 2 . Rate of Weevil Spread i n Young Pine Stands 102 5 - 3 . Weevil Attack Pattern i n Pine Stands 105 6. Studies of the L i f e Stages of H. warreni • I l l 6 . 1 . Larval Stage 111 6 .1 .1 . Larval instar determination 111 6 .1 .2. Feeding pattern and development of larvae 111 6 . 1 . 3 . Bark microhabitat studies 121 6 .1.4. Mortality factors of larvae, pupae and tenerals 121 6.2. Pupal Stage 129 6.3. Adult and Egg Stages 129 6 . 3 . 1 . Numbers of adults and sex rat i o s 129 6 .3 .2. Relationship of trapped adults and tree size 13^ 6 .3 .3. Dispersal patterns of adults i n the forest 13*+ 6.3.I+. Weevil reproduction 138 6 .3-5. Light and temperature response and orientation of adults 1^9 6 . 3 . 6 . Adult feeding patterns 153 6 .3.7. M o r t a l i t y factors of adults 155 7. Studies of the Effects of Weevil Damage to Trees 158 7 . 1 . Anatomical Effects 158 7 . 2 . Growth Loss Effects l64 DISCUSSION 173 v i i i Page SUMMARY 205 CONCLUSIONS 208 LITERATURE CITED 2 l 6 -.ix LIST OF TABLES Page Table I . L i s t o f ground f l o r a l species r e p r e s e n t a t i v e of the 65-70-year o l d pine stand of p l o t s 1 to 5« 58 Table I I . L i s t of ground f l o r a l species r e p r e s e n t a t i v e of average s i t e c o n d i t i o n s . i n the Robb Burn. 59 Table I I I . V e g e t a t i o n a l canopy s t r a t a of four s m a l l p l o t s i n the 65-70-year o l d pine stand. 60 Table IV. Summary of stand d e n s i t y and t r e e diameter/",, (d.s.h.) c h a r a c t e r i s t i c s i n H. warreni sampling p l o t s 1 to 5 during 1961. 62 Table V. Summary of t r e e diameter c h a r a c t e r i s t i c s i n H. warreni sampling p l o t s 1 to 5 during 1962. 63 Table VI . Summary of t r e e diameter c h a r a c t e r i s t i c s i n H. warreni sampling p l o t s 1 to 5 during 1963. 64 Table V I I . C h a r a c t e r i s t i c s of tre e s sampled f o r H. warreni popula-t i o n s i n s e v e r a l p l o t areas of mature p i n e . 65 Table V I I I . The I961 H. warreni populations t a l l i e d by s t r i p i n p l o t s l ' t o 5. 66 Table IX. The 1962 H. warreni populations t a l l i e d by s t r i p i n p l o t s 1 to 5. • 67 Table X. The 1963 H. warreni populations t a l l i e d by s t r i p i n p l o t s 1 to 5- 68 Table X I . Hylobius warreni populations c o l l e c t e d from s e v e r a l plot-areas of mature pine. 69 Table X I I . Comparison of sampled t r e e frequency d i s t r i b u t i o n s ( i n percent) between p l o t groups of d i f f e r e n t w e e v i l i n f e s t a t i o n l e v e l s . 72 Table X I I I . Summary of the'population s t r u c t u r e of H . warreni c o l l e c t e d i n p l o t s 1 to 5 during 1961. 73 Table XIV. Summary of the p o p u l a t i o n s t r u c t u r e of H. warreni c o l l e c t e d i n p l o t s 1 to 5 during 1962. 7^ Table XV. Table XVI. Table XVII. Table XVIII. Table XIX. Table XX. Table XXI. Table XXII. Table XXIII. Table XXIV. Table XXV. Table XXVI. Table XXVII. Summary of the population structure of H. warreni collected i n plots 1 to 5 during 1963. Summary of the population structure of H. warreni collected i n several plots and areas. Calculated "k" values of the negative binomial d i s t r i b u t i o n used as a measure of the degree of aggregation of different weevil populations and habitats. Summary of the tree' and weevil measurements i n pine stands in.the Robb and Ricinus burn areas. Summary of tree frequencies showing weevil density and tree size characteristics. Average duff depth i n inches measured at the base of sampled trees i n plots 1 to 10 . Summary of the percentage of weevil populations found on the root and c o l l a r regions of sampled trees i n plots 1 to 10. Pine regeneration survey on clearcut sites i n the Robb study area. Population indices for pine stands 60+ years old. Summary of H. warreni attack history i n a 6 5 - 7 0 -year old pine stand. Summary of the mortality incidence to immature stages of H. warreni i n plots 1 to 10. Numbers of adults and the sex ratios of H. warreni collected by different methods i n different years i n the 65-70-year old stand. Summary of the r e l a t i v e abundance and recapture characteristics of male and female H. warreni i n plots A and B during 1964-66. Page 75 76 79 82 .82 92 Table XXVIII. Survival of male and female adult H. warreni released i n 1964 i n p l o t arenas C and D. 102 108 108 124 130 135 135 x i Page Table XXIX. Chi square t e s t of d i r e c t i o n a l movement of male and female adult H. warreni i n p l o t s A and B according to a 1:1:1:1:1:1:1:1 r a t i o . 141 Table XXX. Table XXXI. Table XXXII. Summary of t r e e stand, o v i p o s i t i o n and egg hatch c h a r a c t e r i s t i c s i n p l o t s C and D during I965 and I966. Summary of H. warreni egg l a y i n g experiment i n p l a s t i c cages on pine stumps. Summary of the observations of the f a t "body and rep r o d u c t i v e s t r u c t u r e s of female H. warreni c o l l e c t e d during 1964 and I965. 143 146 148 Table XXXIII. Measurements of w e e v i l attacked and non-attacked t r e e s i n the Robb Burn and Grande P r a i r i e study areas. 165 Table XXXIV.. Numbers of l a t e r a l branches on the top whorl of attacked and non-attacked t r e e s i n the Robb Burn and Grande P r a i r i e areas. 165 Table XXXV. Needle length, t e r m i n a l leader and top l a t e r a l branch lengths of attacked and non-attacked trees i n the Robb Burn and Grande P r a i r i e areas. 166 Table XXXVI. Average r i n g t hickness per year and per t r e e group of attacked and non-attacked trees as determined from oblique sequence measurements. 167 x i i LIST OF FIGURES Page Fi g . 1. Map of Alberta showing main study areas, Lower F o o t h i l l s Section and the d i s t r i b u t i o n of jack and lodgepole pine. 10 F i g . 2 . Cut layout map showing H. warreni sample plots 1 to 6 and mark-recapture plots A and B i n the 65-70-year old pine stand near Robb, Alberta. Lower figure i l l u s t r a t e s the d i v i s i o n of a 3~acre sample plot into s t r i p s and blocks. . 15 F i g . 3> Cross-section through a 66-year old pine stump at root c o l l a r l e v e l showing approximate years of weevil attack. 29 F i g . 4 . Trap design used for l i v e trapping adult H. warreni. 35 F i g . 5- Circular-shaped plot C located i n the Robb Burn showing trap attachment and sphagnum moss layer. kl Fig. 6 . Arena and scaffold enclosing two 65-70-year old pine trees used for adult weevil behavioral studies. 46 F i g . 7- Known d i s t r i b u t i o n of Hylobius warreni and H. p i n i c o l a i n western Canada and Alaska. 53 F i g . 8 . Map of Alberta showing the d i s t r i b u t i o n of H. warreni i n r e l a t i o n to the Lower F o o t h i l l s Section. F i g . 9 - Tree diameter frequency d i s t r i b u t i o n of sampled trees i n plots 1 to 5 during 1961. 56 Fig. 10. Hylobius warreni population levels i n di f f e r e n t s t r i p s of plots 1 to 5 during 1961 to 1965. 71 F i g . 11 . Comparison of the structure of H_. warreni l a r v a l popula-tions between years for plots '1 to 5 5 19&1, 1962, 1963 and 1965 and plot 9 , 1966. 78 Fig. 12. Variance plotted against the mean of H. warreni populations per 15 sampled trees, to obtain the constant "a" and "b" values of Taylor's power law. 8 l Figs. 13 and 14. Relationship between weevil numbers per tree and tree diameter size for three different years i n s t r i p s A and B of plots 1 to 5. 84 Figs. 15 and 16. Relationship between numbers of weevils per tree and tree diameter size for four different years i n s t r i p s C and D of plots 1 to 5- 8 5 x i i i Page F i g . 17- R e l a t i o n s h i p between numbers of weevils per t r e e and t r e e diameter s i z e f o r four d i f f e r e n t l e v e l s of abundance. 86 F i g . 18. R e l a t i o n s h i p "between percent t r e e s attacked ( o l d and current a t t a c k s ) and t r e e diameter i n the 20 -25-year o l d stand of p l o t s V I I , V I I I and IX. 87 F i g . 19. R e l a t i o n s h i p between w e e v i l numbers per block and t r e e d e n s i t y per b l o c k i n the 65 -70-year o l d pine stand of p l o t s 1 to 6 . 89 F i g . 20 . Tree d e n s i t y and w e e v i l a t t a c k p a t t e r n i n the regenera-t i o n p l o t s e r i e s V I I , V I I I and IX combined, and p l o t t e d i n r e l a t i o n to d istance from the stand periphery. 90 F i g . 2 1 . Tree d e n s i t y and w e e v i l a t t a c k p a t t e r n i n p l o t X, p l o t t e d i n r e l a t i o n to d istance from the stand periphery. 90 F i g . 22 . R e l a t i o n s h i p between w e e v i l numbers per t r e e and d u f f depth of four t r e e diameter cl a s s e s i n p l o t s 1 to 5- 91 F i g . 2 3 . R e l a t i o n s h i p between w e e v i l numbers per t r e e and d u f f depth of four t r e e diameter classes i n p l o t s 6 and 7- 93 F i g . 24. Frequency d i s t r i b u t i o n s of d u f f depth of four d i f f e r e n t t r e e diameter cl a s s e s i n p l o t s 1 to 5- 9^ F i g / 2 5 . R e l a t i o n s h i p o f numbers of weevils per t r e e and d u f f depth w i t h comparisons f o r three d i f f e r e n t t r e e diameter c l a s s e s i n p l o t s 1 to 5- 95 F i g . 26 . R e l a t i o n s h i p of numbers of weevils per t r e e and d u f f depth w i t h comparisons f o r three d i f f e r e n t t r e e diameter c l a s s e s i n p l o t s 6 and 7- 96 F i g . 2 7 . Graph showing the p r o p o r t i o n a l change of w e e v i l numbers on r o o t s and c o l l a r w i t h i n c r e a s i n g t r e e s i z e . 98 F i g . 2 8 . Frequency d i s t r i b u t i o n of t r e e heights of pine regeneration, 3 - 9-years o l d , i n p l o t VI showing .the p a t t e r n of w e e v i l attacked t r e e s . 103 F i g . 29. Frequency d i s t r i b u t i o n of tree' heights of young pine, 1 5 -year s o l d i n p l o t s e r i e s X ( R i c i n u s Burn), showing the p a t t e r n of w e e v i l attacked t r e e s . 103 x i v Page F i g . 30. Frequency d i s t r i b u t i o n of t r e e diameters of pine, 20 - 2 5 -years o l d (Robb Burn) i n p l o t s V I I , V I I I and IX, and showing the w e e v i l attacked t r e e p a t t e r n . 104 F i g . 31- Comparison of o l d a t t a c k and f r e s h a t t a c k p a t t e r n s i n r e l a t i o n t o t r e e diameter s i z e i n d i f f e r e n t pine stands. 106 F i g . 32 . R e l a t i o n s h i p between w e e v i l numbers per t r e e and percent-t r e e s w i t h f r e s h a t t a c k s . 109 F i g . 33 . H i s t o r y of w e e v i l a t t a c k frequency on small, medium and large t r e e s , 6 5 - 7 0-years o l d , and l o c a t e d between p l o t s 1 to 5. 110 F i g . 34. R a d i a l growth c h a r a c t e r i s t i c s of small, medium and large . w e e v i l attacked t r e e s , 6 5 - 7 0-years o l d and l o c a t e d between p l o t s 1 to 5- 112 F i g . 35- P i c t o r i a l model showing the p r o g r e s s i v e w e e v i l a t t a c k pat-t e r n i n n a t u r a l l y stocked pine stands. 113 F i g . 36. Frequency d i s t r i b u t i o n of Hylobius warreni l a r v a l head capsule width determinations. 114 F i g . 37- R e l a t i o n s h i p between l a r v a l s i z e and average feeding depth i n the bark t i s s u e of 20 - 2 5-year o l d pine t r e e s . 117 F i g . 38- H. warreni l a r v a l feeding wounds on a 65 -70-year o l d pine stump. 118 F i g . 39- F i f t e e n - y e a r o l d pine stump - showing the- c i r c u m f e r e n t i a l pat-tern of l a r v a l feeding. 118 F i g . 40. Comparison of w e e v i l habitat- temperatures at cut-stumps and at non-cut stumps. 120 F i g . 41. R e l a t i o n s h i p between r e s i n pocket diameter and p o s i t i o n ' on the l a t e r a l r o o t s and main stem. 122 F i g . 4 2 . R e l a t i o n s h i p between numbers of bark r e s i n pockets per bark c r o s s - s e c t i o n a l area and p o s i t i o n on the l a t e r a l r o o t s and main stem. 122 F i g . 4 3 . R a t i o of bark r e s i n pocket area to bark area on a t r a n s -verse plane of l a t e r a l r o o t s and main stem. 122 F i g . 44. R e l a t i o n s h i p of bark thickness and p o s i t i o n of the l a t e r a l r o o t s and main stem. 122 XV Page Fig . 45.- Cross-sectional view of a disc cut 4 inches above the root c o l l a r on the main stem of a 21-year old pine showing bark r e s i n pockets. 123 F i g . 46 . Female adult of Dolichomitus tuberculatus tuberculatus (Fourc.) and i t s emergence case. 126 Fig. 4 7 . Two l i v e H. warreni pupae and one dead prepupa i n the presence of the l a r v a l parasite, Dolichomitus tuberculatus tuberculatus. 126 Fig. 48. Dipteran larva collected from the pupal chamber of H. warreni. 128 Fig. 49. Numbers of male and female adult weevils captured throughout the summer of I965 i n plots*A and B. 132 F i g . 50. Numbers of male and female adult weevils captured throughout the summer of 1966 i n plots A and B. 132 F i g . 51. Numbers of male and female adult weevils captured throughout the summer of 1965 i n plots C and D. 133 F i g . 52. Numbers of male and female adult weevils captured throughout the summer of 1966 i n plots C and D. 133 F i g . 53- Frequency d i s t r i b u t i o n of tree diameters i n plots A and B. 136 F i g . 54. Catch frequency of adult male and female H. warreni on dif f e r e n t sized trees i n plots A and B. 136 F i g . 55- Relationship between captured adult weevils and tree diameters i n plots A and B during I965 and 1966. 137 Fig. 56. Frequency of tree size with different numbers of adult captures i n plots A and B during 1965 and 1966. 137 F i g . 57. Rate of dispersion of male and female adult weevils i n plots A and B during I96U, 1965 and 1966. ' 139 Fig. 58. Rate of dispersion of male and female adult weevils separately i n plots A and B. 139 Fig. 59. D i r e c t i o n a l movement of adult male and female weevils i n p l o t A. ' ihO F i g . 60. D i r e c t i o n a l movement of adult male and female weevils i n plot B. 1^0 X V I Page Fi g . 6 l . Frequency di s t r i b u t i o n s of tree diameters i n plots C and D. 142 Fig. 62 . Relationship between numbers of weevil progeny per tree and tree diameter i n plots C and D during 1966. 142 Fig . 63 . Summer egg laying pattern of H. warreni reared i n paper cups inverted over pine bark during 1964. 145 Fig . 64. Percentage egg hatch and the period of embryonic develop-ment of H. warreni eggs. 145 Fig. 65 . Correlation of adult weevils captured i n plots C and D with night temperatures. 150 Fig. 66 . Relationship between adult weevil catch i n plots C and D and temperatures recorded at 11:00 p.m. 150 Fig. 67. D i r e c t i o n a l response of adult H. warreni confined within a 90-cm. diameter arena. ' 152 F i g . 68. Numbers of adult H. warreni emerging from moss i n r e l a t i o n to time during the evening. 152 F i g . 69. Pattern of adult weevil feeding scars on branches i n r e l a t i o n to height-above ground. • . 154 Fig. 70 . Frequency d i s t r i b u t i o n of adult weevil branch feeding scars i n r e l a t i o n to height above ground.. . 154 F i g . J l . Adult weevil-feeding damage oh terminal shoot's of 6 - 8 -year old pine. • . - 156 Fig. 7 2 . Dead adult H. warreni infected with the fungal parasite, . Eeauveria b a s s i a n a . . . . 157 Fig. 7 3 . Nematode parasite (family Tylenchoidea) found within the abdomen of a female adult weevil. 157 F i g . 74-. Cross-sectional view of a 66-year old pine stump showing dated weevil l a r v a l feeding scars and bud-like growth pattern of wood increment. 159 Fig. 75- Wood discs cut at 2-inch intervals up the main stems of •20-year old pine trees showing evidence of traumatic r e s i n ducts (attacked tree) and normal ducts (non-attacked tree). l 6 l X V I I Page F i g . 76 . Enlarged view of a t r a n s v e r s e l y cut d i s c from.a w e e v i l attacked pine stem showing v e r t i c a l traumatic r e s i n ducts. l 6 l ed F i g . 77. . R a d i a l view of the lower stem of a w e e v i l a t t a c k pine t r e e showing resin-soaked sapwood 162 F i g . 78 . Transverse view of d i s c s removed from the taproots of w e e v i l attacked and non-attacked tr e e s showing resin-soaked sapwood. l62 F i g . 79 - Lower stem of a 15-year o l d pine showing a d v e n t i t i o u s root development above a w e e v i l larvaL wound. 163 F i g . 80. Lower stem of a 95-100.-year o l d pine showing a d v e n t i t i o u s r o o t development-above a w e e v i l l a r v a l wound. ' 163 F i g . ' 8 l . Oblique growth sequence patt e r n s of attacked and non-attacked t r e e s from the Robb Burn. 168 F i g . 82. Oblique growth sequence p a t t e r n s of attacked and non-attacked t r e e s from the Grande P r a i r i e . a r e a . 169 F i g . 83 . R a d i a l growth sequence patt e r n s of attacked and non-• ' attacked trees from the Robb Burn. - 171 F i g . 8k. Radial.growth sequence patt e r n s of attacked and non-attacked t r e e s from.the Grande P r a i r i e . a r e a . - 171 F i g . 85 . Vertical''growth sequence patt e r n s o f attacked and non-attacked t r e e s from the Robb Burn. . 172 F i g . 86. " V e r t i c a l growth sequence p a t t e r n s of attacked and non-attacked trees from the Grande'Prairie area. 172 INTRODUCTION The root w e e v i l , Hylobius warreni Wood i s an indigenous pest to f o r e s t s i n Canada and the eastern U n i t e d States (Warren 1956c; Finnegan 1962b; Warner 1966). I t feeds upon v a r i o u s coniferous hosts i n a wide range of e c o l o g i c a l s i t u a t i o n s (Reid 1952; Ross 1955; Stark 1959b; Warren and P a r r o t t 1965; Grant 1966). During i t s l a r v a l stage t h i s i n s e c t mines the phloem and cambial t i s s u e s , causing l a r g e open wounds at the ro o t c o l l a r and roo t s of i t s host trees (Reid 1952; Warren 1956b) . Trees are i n j u r y s u s c e p t i b l e to att a c k at ages from a few years to maturity, b u t ^ i s most severe i n the more vigorous t r e e s i n the dominant, co-dominant and intermediate c l a s s e s (Reid 1952) . U n l i k e most other bark-cambium feeders the w e e v i l r e q u i r e s no apparent pre-weakening of i t s host f o r s u c c e s s f u l a t t a c k . The s u s c e p t i b i l i t y of tre e s i n n e a r l y a l l age categories i n d i c a t e a wide range of tol e r a n c e s i n the wee v i l ' s s e l e c t i o n of h a b i t a t . I n A l b e r t a r e p o r t s of t r e e m o r t a l i t y from w e e v i l feeding over the past 15 years have been frequent, but included t r e e s l e s s than three inches i n diameter almost e x c l u s i v e l y . The w e e v i l , however, has never been reported i n such abundance as to be termed epidemic, except perhaps i n pine p l a n t a t i o n s ( D a v i a u l t 19^9; Finnegan 1962b; Warren 1956c; Warren and P a r r o t t 1965) . These f a c t s pose two e s s e n t i a l e c o l o g i c a l questions which are o f immediate concern to f o r e s t management. The f i r s t question i s what f a c t o r s are r e s p o n s i b l e f o r the weevil's s p a t i a l v a r i a b i l i t y i n abundance i n f o r e s t e d areas? The second question i s what f a c t o r s are r e s p o n s i b l e f o r the weevil's apparent o v e r a l l numerical r e s t r a i n t and s t a b i l i t y ? - 2 -In t h i s thesis e s s e n t i a l l y four main aspects are studied to provide answers to these questions. The f i r s t aspect i s the geographical d i s t r i b u t i o n of H. warreni within the natural range of i t s host species. A second aspect i s concerned with annual weevil abundance and population structure within a variety of stand conditions. A t h i r d aspect i s concerned with the behavior of the l i f e stages of the weevil. This information increases the understanding of the weevil i n r e l a t i o n to i t s host tree and to other factors of i t s environment. The fourth aspect i s concerned with the impact of weevil feeding upon the host tree, and how th i s may ultimately affect the stand as a whole. 1 . H i s t o r i c a l Review The f i r s t collections of adult H. warreni i n western Canada were probably made during the 1930's, but concern for i t s damage to forest trees did not develop u n t i l about 1950. This was largely due to the insidious nature of the weevil and to the fact that forest insect surveys became i n t e n s i f i e d only after the mid-19^-0's. Insects attacking roots of trees were often overlooked. Widespread occurrence of the weevil was noted i n Quebec ( i d e n t i f i e d as Hypomolyx piceus) by Daviault (19^-9) a n d later i n Manitoba by Warren and Whitney (T95l)> and by Reid (1952) i n Alberta. These reports indicated a wide d i s t r i b u t i o n pattern extending across most of Canada, and showed that several commercially important coniferous species were involved. The weevil's extensive d i s t r i b u t i o n , i t s preferred hosts and feeding damage characteristics demonstrated the need for investigations on - 3 -the b i o l o g y of the w e e v i l , and an e c o l o g i c a l and economic e v a l u a t i o n of i t s damage p o t e n t i a l . This need was i n t e n s i f i e d when i t was discovered that Hylobius wounds provide an important avenue of i n f e c t i o n f o r root' r o t t i n g and s t a i n i n g f u n g i i n spruce (Warren and Whitney 1951;. Whitney 1952; Whitney 1961). Whitney (1962) a l s o showed that the wounds were a s i g n i f i c a n t f a c t o r i n the development of stand-opening disease of spruce. I n t e n s i v e s t u d i e s i n i t i a t e d by Warren on H. warreni i n Manitoba and Saskatchewan provided b a s i c i n f o r m a t i o n on l i f e h i s t o r y , morphology and s i t e f a c t o r s a s s o c i a t e d w i t h w e e v i l populations (Warren 1956b, 1956d, 1958, 1960a, 1960b). The studies of Reid (1952) and Stark (1959b) i n A l b e r t a are complementary to those of Warren. Warren (1956b, 1956c) f i r s t drew a t t e n t i o n to an important aspect of w e e v i l damage to tre e s which he described as cumulative w i t h each successive a t t a c k . He developed a damage a p p r a i s a l system to survey stands on the b a s i s of an accumulative "Damage Index". This a p p r a i s a l system, however, has c e r t a i n l i m i t a t i o n s f o r use i n b i o l o g i c a l e v a l u a t i o n i n t h a t i t deals i n d i r e c t l y w i t h w e e v i l p o p u l a t i o n s . E s s e n t i a l l y no s t u d i e s were undertaken to f o l l o w w e e v i l populations from year to year and thereby gain an i n s i g h t i n t o f a c t o r s which may l i m i t p o p u l a t i o n i n c r e a s e . Estimates of w e e v i l numbers per t r e e were made i n lodgepole pine stands by Stark (1959b) but l i t t l e attempt was made to r e l a t e pine f o r e s t c o n d i t i o n s to l e v e l s of w e e v i l abundance. The s t u d i e s of Warren i n Manitoba were c a r r i e d out p r i m a r i l y In white spruce, P i c e a glauca (Moench) Voss and i n jack pine, Pinus banksiana Lamb, while those of Reid (1952) and Stark (1959b) i n A l b e r t a apply mostly to lodgepole pine, Pinus c o n t o r t a Dougl. var. l a t - i f o l i a Engelm. The l a t t e r - h -two authors observed t h a t H. warreni showed d i s t i n c t preference f o r lodgepole pine over white spruce, where the two species were growing together n a t u r a l l y . In.a stand 95 percent of the pine component had w e e v i l scars (Reid 1952) and appeared to support n e a r l y a l l of the w e e v i l p o p u l a t i o n . These f a c t s open up the p o s s i b i l i t y t h a t i n f o r m a t i o n gathered i n spruce h a b i t a t s may not w h o l l y apply i n lodgepole pine stands. Coincident w i t h the increased usage of lodgepole pine as a primary pulpwood species i n A l b e r t a and B r i t i s h Columbia i s the need f o r an understanding of the s i l v i c a l and economic e f f e c t s of w e e v i l damage to t h i s host. This need p a r a l l e l s the increased emphasis placed upon f o r e s t p r o t e c t i o n . I n the b i o l o g i c a l sense i t i s of i n t e r e s t to a s c e r t a i n the i n t r i n s i c and e x t r i n s i c f a c t o r s which a f f e c t the weevil's abundance since t h i s allows p r e d i c t i o n s to be made i n "new" f o r e s t s i t u a t i o n s . Few comprehensive studies of Hylobius populations are known i n North America, Europe and A s i a (Nordic F o r e s t Entomologists' Research Group 1962; M i l l e r s 1965; Matsuzawa, e t , a l . 1963) . These studies of H. warreni were conducted by the author during the p e r i o d 1961 to 1966 i n c l u s i v e . They are of a research p r o j e c t w i t h the Forest Research Branch of Canada Department of F o r e s t r y and R u r a l Development, being c a r r i e d out i n the f o o t h i l l s r e g i o n of the Rocky Mountains i n A l b e r t a . - 5 -MATERIALS AND METHODS 1. The Study I n s e c t The experimental animal used throughout t h i s study was Hylobius  warreni . I t s taxonomic d e s c r i p t i o n , l i f e h a b i t s and known hosts are b r i e f l y reviewed and comparative i n f o r m a t i o n i s given on a c l o s e l y r e l a t e d species, H. p i n i c o l a . The s i m i l a r i t i e s and d i f f e r e n c e s between the two species are pointed out because of taxonomic problems encountered by previous authors (Wood 1957) . I . 1 Taxonomy: The r o o t w e e v i l , H. warreni i s the l a r g e s t and perhaps most-widespread of seven species of the genus i n North America, a l l of which are coniferous feeders (Warner I966). P r i o r to 1957 there was u n c e r t a i n t y about the c o r r e c t taxonomic status of H. warreni. The i n i t i a l s t u d i e s of Warren i n Manitoba r e v e a l e d two a d u l t forms. One was d i s t i n g u i s h e d by w e l l developed metat-horacic wings, the other.by a. v e s t i g i a l form of hind wing. These two forms were f i r s t b e l i e v e d to be a dimorphism of the same species and were i d e n t i f i e d as Hypomolyx piceus (De Geer), after, the E u r a s i a n species. Both forms were c o l l e c t e d from e s s e n t i a l l y the same spruce h a b i t a t s and only minor d i f f e r e n c e s i n e x t e r n a l morphology were observed. Wood (l957)> however, i n v a l i d a t e d the genus Hypomolyx of Leconte and separated the E u r a s i a n species, Hylobius piceus, from the Hylobius "complex" of Warren. Wood showed t h a t two d i s t i n c t species were present i n Warren's m a t e r i a l . The form w i t h well-developed hind wings was Hylobius p i n i c o l a Couper while the v e s t i g i a l winged-form was designated a new species, Hylobius warreni Wood. I n a l a t e r comprehensive study Warren (1960b) presented a d e t a i l e d - 6 -d e s c r i p t i o n of the e x t e r n a l morphology of H. p i n i c o l a and H. warreni. Manna and Smith (1959) provided strong c y t o l o g i c a l evidence t h a t these two species a l s o d i f f e r e d i n chromosomal counts. Taxonomic keys f o r North American species of Hylobius a d u l t s have been provided by Wood (1957) , Finnegan (1961) , M i l l e r s , et a l . (1963) and Warner (1966). No key i s yet a v a i l a b l e to separate the immature stages of H. warreni from H. p i n i c o l a . A search of the l i t e r a t u r e suggests t h a t r e l a t i v e l y few species are represented i n the genus Hylobius throughout the. northern hemisphere; seven i n North America (Warner 1966) , four i n Europe (Scherf 1964) and s e v e r a l i n A s i a , i n c l u d i n g Japan (Manna and Smith 1959j Morimoto I962, Takenouchi 1963)• 1 .2 l i f e Stages and H a b i t s : This d e s c r i p t i o n o f the l i f e stages o f H. warreni i s summarized from the r e p o r t s o f Reid (1952) , Warren (1956b) and Star k (1956b) and p e r t a i n to con d i t i o n s i n the A l b e r t a f o o t h i l l s . The l i f e h i s t o r y of the w e e v i l i s not completely understood, being complicated by an overlap of generations. The p e r i o d from egg to adult extends approximately two years. O v i p o s i t i o n occurs from June to September and eggs are deposited i n the r o o t - c o l l a r zone o f the host t r e e . When f r e s h l y l a i d the eggs are', p e a r l y white and e l l i p s o i d a l . They appear to hatch by September and overwinter i n the l a r v a l stage. The number of i n s t a r s i s u n c e r t a i n but seven were recorded from a r t i f i c i a l r e a r i n g s (Warren 1960a) . On the b a s i s of head capsule width measurements Stark (1959b) determined s i x . The l a r v a e feed upon the phloem and cambial t i s s u e s i n the r o o t -c o l l a r zone, causing continuous r e s i n o s i s . Development of l a r v a e terminates between mid-June and mid-July a f t e r a feeding p e r i o d of about two years. At - 7 -t h i s time the mature larva constructs a special chamber from r e s i n and bark frass i n which i t transforms to a prepupal, pupal and teneral stages. Larvae remain on the same tree throughout the i r development. Transformation to the pupal stage takes about two weeks, l a s t s three to four weeks and ends with adult eclosion, usually i n August. Similar observations were noted by Daviault (1949) i n southern Quebec for the same weevil. The resinous chamber serves to protect the prepupa, pupa and young adult u n t i l the time of emergence during the l a t t e r part of August and early September. The studies of Stark ( l 9 5 9 a ) suggested that the weevil may overwinter i n a l l stages of the l i f e cycle. The adult at maturity i s robust i n form, ranging i n length from 1 1 . 7 to I 5.I mm. (Wood 1957) ; i t s beak i s moderately elongated. I t i s reddish black i n color and f l i g h t l e s s , with greatly reduced metathoracic wings and wing supporting structures. The adult stage may extend one or more years including at least two overwintering periods. New adults are added to the population pool annually. This results i n v a r i a t i o n of age d i s t r i b u t i o n from one year to the next. Egg laying may extend over one or more summers for i n d i v i d u a l females. The adults are mostly nocturnal i n habit. At night they disperse l a t e r a l l y between trees and ascend tree trunks. They return to the forest l i t t e r before sunrise where they generally remain throughout the day. 1 .3 Host Species and Geographical Di s t r i b u t i o n: Collections of adult H. warreni and H. p i n i c o l a indicate that they are distributed i n a similar pattern i n North America but may be separated largely by host and habitat preference. H. p i n i c o l a has been found predominantly i n moist swampy habitats on the hosts, tamarack, Larix l a r i c i n a (Du Rei) K. Koch, black spruce, Picea mariana ( M i l l . ) BSP., white spruce (Warren 1956b; Wood 1957; Grant 1966) and balsam - 8 -f i r , Abies balsamea (L.) M i l l . (Smerlis 1957, 1 9 6 l ) . The primary hosts of H. warreni include lodgepole pine, jack pine, white spruce and western white pine, Pinus monticola;: Dougl. (Reid 1952; Ross 1955; Warren 1956b; 1960b; Grant 1966). Additional hosts include black ._••<. spruce, red pine (Pinus resinosa A i t . ) and Scots pine (P. s y l v e s t r i s L.). Plantations -of the l a t t e r two pine species i n Newfoundland and southern Quebec were found p a r t i c u l a r l y susceptible to H. warreni attack (Daviault 19^ +9? Finnegan 1962b; Warren and Parrott 1965) . The geographical di s t r i b u t i o n s of H. warreni and H. p i n i c o l a are described for north western America to indicate t h e i r s p a t i a l overlap, and to define p o t e n t i a l forest problem areas. Collections of adult weevils were used for the preparation of d i s t r i b u t i o n maps. A l l areas .lying within the natural range of lodgepole pine i n western Canada and the United States were consideredj including some adjacent areas i n Alberta and the Northwest T e r r i t o r i e s . In addition to specimens collected i n Alberta, information on d i s t r i b u t i o n records was requested from museums and forest research laboratories i n western Canada and the U.S. 2 . Studies of Hylobius Populations The general problem underlying the weevil studies had three aspects. The f i r s t was to ascertain population patterns of abundance, t h e i r change with time and th e i r correlation with stand conditions. The second was to ascertain the nature and extent of casualty factors operating on diff e r e n t stages i n the l i f e cycle of the insect. The t h i r d was to ascertain the effects of weevil injury on the host trees. Population patterns were considered to be most l i k e l y related to - 9 -stand maturity, h a r v e s t i n g p r a c t i c e s , t r e e s i z e , stand d e n s i t y and d u f f t h i c k n e s s . The age of the stand was considered important since most areas of lodgepole pine have regenerated i n an even-age c o n d i t i o n . I t was t h e r e f o r e necessary to determine the age of young stands when i n i t i a l w e e v i l i n v a s i o n occurs, and to f o l l o w the subsequent changes i n p o p u l a t i o n p a t t e r n s through to stand m a t u r i t y . This n e c e s s i t a t e d sampling f o r w e e v i l populations i n a v a r i e t y of even-aged pine stands. The method of c l e a r c u t t i n g i s most w i d e l y used i n the harvest of lodgepole pine and t h i s p r a c t i c e was incorporated i n t o the o v e r a l l design of a sampling p l a n . Tree s i z e , t r e e d e n s i t y and d u f f depth are measurable v a r i a b l e s which help to define the p h y s i c a l s t r u c t u r e of the w e e v i l h a b i t a t . The term " d u f f " as used here' i s defined as the l i v i n g and dead organic matter i measured to the depth of m i n e r a l s o i l . To a s c e r t a i n p o p u l a t i o n p a t t e r n s of abundance•it was necessary to choose s u i t a b l e areas to represent the d e s i r e d stand c o n d i t i o n s , to design a sampling p l a n , to choose techniques of observations and to apply appropriate s t a t i s t i c a l methods of a n a l y s i s . Weevil populations as used i n the context of t h i s t h e s i s r e f e r s to numbers of weevils per p l o t area or t o t a l numbers of weevils on a l l t r e e s w i t h i n s p e c i f i e d p l o t areas. 2 . 1 . Study Areas:- Weevil studies were concentrated i n two main areas of A l b e r t a . These were ( l ) Robb study area and (2) Rocky Mountain House study area ( F i g . l ) . Both areas l i e w i t h i n the Lower F o o t h i l l s S e c t i o n of the B o r e a l F o r e s t Region (Rowe 1959). The reasons f o r the choice of the Lower F o o t h i l l s were s e v e r a l . C o l l e c t i o n s made p r i o r to i960 i n d i c a t e d t h a t H. warreni occurred more commonly i n pine stands at lower e l e v a t i o n s of the A l b e r t a f o o t h i l l s than at higher e l e v a t i o n s . Other reasons relate- to the F i g . 1 . Map of A l b e r t a showing main study areas, Lower F o o t h i l l s S e c t i o n and the d i s t r i b u t i o n s of jack and lodgepole p i n e . The overlap of d i s t r i b u t i o n s of the two pine species i n west c e n t r a l A l b e r t a was defined as a h y b r i d i z a t i o n zone (Moss 1953) . Study areas 1, 2 and 3 are Robb, Rocky Mountain House and Grande P r a i r i e r e s p e c t i v e l y . - 10 -- 1 1 - -n a t u r a l d i s t r i b u t i o n o f l o d g e p o l e p i n e ( F i g . l ) , and t o i t s c o m m e r c i a l v a l u e s w i t h i n t h e Lower F o o t h i l l s S e c t i o n . The f o l l o w i n g d e s c r i p t i o n summarizes t h e g e n e r a l a s p e c t s o f the Lower F o o t h i l l s w h i c h a r e c o n s i d e r e d p e r t i n e n t t o t h e s t u d i e s o f H. w a r r e n i . 2 . 1 . 1 . D e s c r i p t i o n o f Lower F o o t h i l l s S e c t i o n : The c r i t e r i a d e f i n i n g the i Lower F o o t h i l l s S e c t i o n were o u t l i n e d b y Rowe (1959) a n d i n c l u d e s 54 p e r c e n t o f t h e t o t a l l o d g e p o l e p i n e f o r e s t e d a r e a i n A l b e r t a ( S m i t h e r s 1962) . The i m p o r t a n c e o f t h i s a r e a i s i n d i c a t e d b y t h e e x i s t e n c e o f one p u l p m i l l c u r r e n t l y i n o p e r a t i o n and t h r e e more p l a n n e d f o r f u t u r e development; a l l w i l l p r o v i d e management o f p i n e f o r e s t s w i t h i n t h e Lower F o o t h i l l s S e c t i o n . N e a r l y a l l s t u d i e s o f t h e w e e v i l were c a r r i e d o ut w i t h i n t h i s s e c t i o n . The d i s t i n c t i v e t r e e s p e c i e s i n t h e Lower F o o t h i l l s i s l o d g e p o l e p i n e w h i c h o c c u r s i n p u r e s t a n d s and i n a d m i x t u r e w i t h o t h e r s p e c i e s . A c c o r d i n g t o H o r t o n (1956) , aspen, P o p u l u s t r e m u l o i d e s M i c h x . , and t o a l e s s e r e x t e n t , b a l s a m p o p l a r , P. b a l s a m i f e r a L. compete w i t h l o d g e p o l e p i n e as p o s t - f i r e pioneers-. I n o l d e r s t a n d s w h i t e and b l a c k s p r u c e a r e common c o n s t i t u e n t s w h i l e a l p i n e f i r , A b i e s l a s i o c a r p a (Hook.) N u t t . i s c o m p a r a t i v e l y r a r e . S c a t t e r e d t h r o u g h o u t t h i s s e c t i o n a r e p o c k e t s o f bog a r e a s w h i c h s u p p o r t b l a c k s p r u c e and tamarack. I n A l b e r t a l o d g e p o l e p i n e has been b r o a d l y termed t h e dominant s u b c l i m a x s p e c i e s (Rowe 1959) 3 a n-d Bloomberg (1950) and Cormack (1953) have i n d i c a t e d t h a t d u r i n g s e c o n d a r y f o r e s t s u c c e s s i o n t h e r e i s a g e n e r a l t r e n d on t h e e a s t s l o p e o f t h e R o c k i e s f r o m l o d g e p o l e p i n e , f o l l o w i n g f i r e , t o a s p r u c e - f i r c l i m a x . F a r t h e r t o t h e n o r t h and e a s t where mixedwood components p r o v i d e a more complex s i t u a t i o n , a s u c c e s s i o n a l t r e n d f r o m p i n e and aspen t o s p r u c e i s s t i l l r e c o g n i z a b l e (Moss 1953). However, t h r o u g h o u t - 12 -the Lower F o o t h i l l s immature pine and aspen stands predominate today, and stands over 100 years of age are rare. (Horton 1956) . According to Horton f i r e has been the major h i s t o r i c f a c t o r which has determined f o r e s t composition and succession. Climax f o r e s t s are r a r e l y a t t a i n e d and t h e r e f o r e succession has l i t t l e s i g n i f i c a n c e i n determining t r e e composition. Factors other than f i r e , e s p e c i a l l y logging, have been of secondary and l o c a l i z e d importance, and only i n the Lower F o o t h i l l s S e c t i o n . H i s t o r i c a l l y there has been a l a r g e demand f o r pine t i e s and p o l e s . These have g e n e r a l l y been s e l e c t i v e l y harvested from a c c e s s i b l e mixedwood stands, l e a v i n g behind p a r t i a l l y cut stands of v a r y i n g d e n s i t i e s . This form of stand opening has o f t e n i n i t i a t e d "two-aged" pine stands or encouraged i n v a s i o n of aspen. The p a t t e r n of pine f o r e s t s i n the A l b e r t a f o o t h i l l s is', l i k e l y to change consid e r a b l y i n f u t u r e years w i t h expansion of the pulpwood economy. I n d i c a t i o n s at present p o i n t to a f a i r l y i n t e n s i v e management of lodgepole f o r e s t s i n eVen age stands w i t h a r o t a t i o n a l p e r i o d of about 80 years or l e s s . F o rest f i r e s have been of v a r y i n g i n t e n s i t i e s , ranging from intense ground f i r e s where a l l v e g e t a t i o n i s k i l l e d , to l i g h t ground f i r e s where considerable p l a n t l i f e has su r v i v e d . F i r e s of the l a t t e r have been described as very common i n the Lower F o o t h i l l s (Smithers I962) , and have given r i s e to many "two-aged" stands. Often pockets of unburned timber as w e l l as i n d i v i d u a l t r e e s remain unharmed i n burned over areas. These undoubtedly have provided " r e s e r v o i r s " f o r s u r v i v i n g Hylobius p o p u l a t i o n s . The topography of the Lower F o o t h i l l s S e c t i o n c o n s i s t s of low h i l l s and plateaux between 3000 and 4000 f e e t i n e l e v a t i o n i n the south and down to 2500 f e e t f a r t h e r north. Throughout t h i s s e c t i o n lodgepole pine has been found to be a h i g h l y adaptable species, occupying a l l s o i l s i t e s from wet to - 13 -extremely dry. Horton (1958) noted that the wide a d a p t a b i l i t y of t h i s s p e c i e s ' r o o t i n g system was l a r g e l y r e s p o n s i b l e f o r i t s s u c c e s s f u l establishment. The major r i v e r systems .flow eastward and v a l l e y s are o f t e n broad. G l a c i a l d r i f t of v a r i a b l e composition occurs most commonly and greywooded or r e l a t e d p o d z o l i c types c h a r a c t e r i z e the s o i l p r o f i l e development-.(Rowe 1959) . During the growing months of May to August i n c l u s i v e the average t o t a l p r e c i p i t a t i o n has been determined as 9 - 1 inches, w h i l e the average annual p r e c i p i t a t i o n i s 17 .7 inches (Smithers 1962) . Included w i t h the Lower F o o t h i l l s S e c t i o n i n A l b e r t a are four out-l y i n g r e g i o n s ; P e l i c a n Mts., Caribou Mts., Clear H i l l s and Cypress H i l l s . These are defined by the same or s i m i l a r c h a r a c t e r i s t i c f e a t u r e s . I n a d d i t i o to the prevalent mixedwood types and .elevation range, c e r t a i n ground f l o r a l species were considered as important i n d i c a t o r s of the Lower F o o t h i l l s , namely Vaccinium m y r t i l l o i d e s , Maianthemum canadense and A r a l i a n u d i c a u l i s (Horton 1956) . ( i ) Robb Study Area; I n v e s t i g a t i o n s of the w e e v i l were most intens near Robb because t h i s area provided a range of stand c o n d i t i o n s i n respect-to ages from current year seedlings to 65 -70-year o l d stands. A l l p l o t s e s t a b l i s h e d here were w i t h i n a r a d i u s of 10 miles aid were s i t u a t e d i n e s s e n t i a l l y even-aged pine stands. A l l stands are w i t h i n the boundary of a pulp lease under management by North Western Pulp and Power L i m i t e d at Hint-on, A l b e r t a . I n a d d i t i o n , c l e a r c u t t i n g operations i n the v i c i n i t y provided the o p p o r t u n i t y -to determine the e f f e c t s of t r e e removal upon the s u r v i v a l of w e e v i l p o p u l a t i o n s , and hence, to evaluate c l e a r c u t t i n g as a - Ik -method of w e e v i l c o n t r o l . Root weevils were f i r s t reported r e l a t i v e l y abundant i n the Robb area i n 1955-56, and i n 1957 an area, was set aside f o r studying Hylobius p o p u l a t i o n s . This area, shown i n Figure 2 c o n s i s t s of a 65 -70-year o l d stand which was surveyed f o r the c l e a r c u t removal of pulpwood i n an a l t e r n a t e s t r i p p a t t e r n . Because of i t s i n t e n s i v e coverage, age and apparent u n i f o r m i t y of s i t e , i t was chosen f o r the major p o p u l a t i o n s t u d i e s . Sampling p l o t s 1 to 6 were l o c a t e d w i t h i n i t s boundaries. The area e n c l o s i n g p l o t s 1- to 5 i s a p l a t e a u which slopes g e n t l y to the southeast and extends f o r about one m i l e . I t s a l t i t u d e i s 3500 f e e t above sea l e v e l . The f o r e s t cover type c o n s i s t s of a uniform stand of e s s e n t i a l l y pure pine w i t h a s c a t t e r e d i n t e r m i x t u r e of white and bl a c k spruce, a S a l i x species and sm a l l i s o l a t e d pockets of aspen. A l l intermixed species except aspen are w e l l below the pine canopy l e v e l . The present stand i s of f i r e o r i g i n and a few remnant pine 90+ years of age were found. These suggest that f i r e had been intense i n both crown and ground l e v e l s . F u rther observations were made to describe the w e e v i l h a b i t a t i n greater d e t a i l . This i n f o r m a t i o n i s supplementary to th a t given f o r the Lower F o o t h i l l s S e c t i o n . Increment borings were made to determine stand age. T o t a l counts of l i v i n g pine t r e e s w i t h i n p l o t areas provided estimates of stand d e n s i t y . F e l l e d t r e e s cut during pulpwood removal were measured f o r average stand height. The t r e e diameters and frequency d i s t r i b u t i o n s of diameters were recorded f o r 800 randomly chosen t r e e s . I n a l l cases, diameter measurements were made at the 1 0-inch stump height (=d.s.h.). F i v e s o i l p i t s , one l o c a t e d w i t h i n each of p l o t s 1 to 5 were F i g . 2 . Cut layout map showing H. warreni sample p l o t s 1 to 6 and mark-recapture p l o t s A and B i n the 65 -70-year o l d pine stand near Robb, A l b e r t a . Lower f i g u r e i l l u s t r a t e s the d i v i s i o n of each 3-acre p l o t i n t o k l o n g i t u d i n a l s t r i p s , each subdivided i n t o k b l o c k s . . Shaded areas i n d i c a t e c l e a r c u t p o r t i o n s . - 15 -STRIPS 1 1 > 1 1 ! " " T T"" i D C OUTLINE B BOUNDARY A 4 3 2 ! <-BLOCKS S C A L E : I CM. = I CHAIN E N L A R G E M E N T OF HYLOBIUS SAMPLING P L O T S 1-7 - 16 -excavated to measure and describe the s o i l p r o f i l e c h a r a c t e r i z i n g the present pine stand. The p r o f i l e s a l s o served as an i n d i c a t o r o f s i t e and s o i l drainage p a t t e r n s . The f i v e p r o f i l e s were combined f o r an average d e s c r i p t i o n of the stand. Horizon d e s c r i p t i o n s and s o i l p r o f i l e c l a s s i f i c a t i o n were adapted from terminology of the r e p o r t of the Meeting of the N a t i o n a l S o i l Survey Committee of Canada ( i 9 6 0 ) . Color d e s c r i p t i o n s were made according to a Munsell Book o f Color. Near the center of the stand were l o c a t e d four c i r c u l a r p l o t s , each 10 f e e t i n diameter. These were examined f o r the t o t a l f l o r a l species complex growing.within them. The species are considered r e p r e s e n t a t i v e of the stand. They were i d e n t i f i e d and an estimate of the r e l a t i v e abundance of each was made according to four c a t e g o r i e s . These were judged according to t h e i r presence or absence i n a l l four p l o t s . The categories were: V.A. = very abundant; C. = common; ' F . C = f a i r l y common; S. = s c a t t e r e d or scarce. Using the most abundant p l a n t species, v a r i o u s canopy s t r a t a were recognized and described to i n d i c a t e the three-dimensional aspect of the w e e v i l h a b i t a t . The percentage of ground surface coverage was estimated f o r three dominant p l a n t groups. The degree of f o r e s t f l o o r l e v e l n e s s was evaluated because of i t s i n f l u e n c e upon co n d i t i o n s i n the w e e v i l h a b i t a t which r e l a t e to surface run-o f f , a d u l t w e e v i l movement, and i n p r o v i d i n g niches f o r predators. Surface l e v e l n e s s was evaluated by extending a cord p a r a l l e l to the ground surface. V e r t i c a l measurements of distances between the cord and -the bottom of a l l depressions were made as w e l l as measurements of a l l h o r i z o n t a l distances between the centers of depressions. An average of these two sets of measurements provided estimates of the degree of undula t i o n . - 17 -A l l s t a n d s sampled f o r H. w a r r e n i p o p u l a t i o n s i n t h e Robb a r e a a r e r e c o r d e d b e l o w a c c o r d i n g t o p l o t numbers and b r i e f d e s c r i p t i o n s ' a r e i n c l u d e d . P l o t s 1 - 6 : P l o t s 1 t o 5 sampled i n 1961, 1962, 1963 and 1965; p l o t 6 sampled i n 1961, 1962, and .1963. P l o t 7: S t a n d age, c o m p o s i t i o n and o r i g i n s i m i l a r t o t h e a r e a o f p l o t s 1 t o 6; l o c a t e d 10 m i l e s west o f p l o t s 1 t o 6; sampled i n 1962 and 1963. . P l o t 8 : L o c a t e d one m i l e n o r t h o f p l o t s 1 t o 6 ; s t a n d o r i g i n , age and c o m p o s i t i o n s i m i l a r t o a r e a o f p l o t s 1 t o 6 . D u r i n g t h e t r e e h a r v e s t i n g o p e r a t i o n o f 1957-58 t h i s s t a n d was c l e a r c u t e x c e p t f o r r e g u l a r l y spaced seed b l o c k s ( e a c h b l o c k measured about 130 f t . ) i n w h i c h no t r e e s were removed. S c a r i f i c a t i o n t r e a t m e n t was a p p l i e d t o t h e c u t o v e r p o r t i o n s i n J u l y , i 9 6 0 , and moderate s t o c k i n g o f p i n e f o l l o w e d . Two seed b l o c k s s e p a r a t e d by a d i s t a n c e o f 600 f t . were sampled f o r w e e v i l p o p u l a t i o n s i n 1963. The seed b l o c k s were c l e a r c u t d u r i n g t h e w i n t e r o f 1963-64 . P l o t 9 : . L o c a t e d i n 6 5 - 7 0-year o l d p i n e a d j a c e n t t o p l o t 1 ; sampled i n 1966. R e g e n e r a t i o n P l o t S e r i e s I , I I , I I I and I V : P l o t s e r i e s I and I I were l o c a t e d i n t h e c l e a r c u t a r e a s u r r o u n d i n g p l o t 8 . The p i n e was 3 - 8 y e a r s o l d i n 1966 and o r i g i n a t e d f r o m n a t u r a l s e e d i n g f o l l o w i n g s c a r i f i c a t i o n . The f o r e s t e x t e n d i n g f r o m t h e boundary c o n s i s t e d o f 6 5 - 7 0-year o l d . p i n e w i t h a p r o m i n e n t u n d e r s t o r y o f b l a c k s p r u c e ; w e e v i l i n c i d e n c e was common. S e r i e s I I I and I V were l o c a t e d near p l o t s 1 t o 6 i n an a r e a c l e a r c u t i n an a l t e r n a t e s t r i p p a t t e r n i n 1959- The c u t a r e a s were s c a r i f i e d i n i 9 6 0 . Good s t o c k i n g o f p i n e f o l l o w e d and t h e t r e e s were 2 - 6 y e a r s o l d i n 1966. The r e s i d u a l s t r i p s s t i l l s t a n d and c o n s i s t o f 6 5 - 7 0-year o l d p i n e w i t h a l i g h t t o heavy u n d e r s t o r y o f b l a c k s p r u c e . - 18 -Regeneration P l o t s V and VI: These were d e l i n e a t e d and sampled i n I966 w i t h i n the same c l e a r c u t area as p l o t s . I and I I . P l o t V extends from the stand p e r i p h e r y and was e s t a b l i s h e d to f o l l o w w e e v i l incidence over a p e r i o d of years; only attacked t r e e s have been t a l l i e d so f a r . P l o t VI was l o c a t e d f a r t h e r w i t h i n . Regeneration P l o t S e r i e s V I I , V I I I , and IX: These p l o t s e r i e s were lo c a t e d i n a 2 0 - 2 5-year o l d pine stand surrounded by a 60~90-year o l d stand. The stand l i e s about 10 miles west of p l o t s 1 to 6 . The stand o r i g i n i s from a f i r e which burned over approximately 1000 acres i n 1941; the area has since been termed the Robb Burn. This area has regenerated by n a t u r a l means to almost pure pine w i t h i n a p e r i o d of about seven years since the f i r e (Baranyay and Stevenson 1964). I n recent years the development of a b l a c k spruce understory has become n o t i c e a b l e i n many regions and aspen i s s c a t t e r e d throughout. A b r i e f d e s c r i p t i o n o f the physiographic features of the area has been given by Baranyay and Stevenson (1964) who s t u d i e d the d i s t r i b u t i o n and abundance of pathogenic diseases and other damaging agents a f f e c t i n g the p i n e . From a s e r i e s of seven permanent p l o t s s c a t t e r e d throughout the burn these authors have examined the root systems of a l a r g e number of dead and dying pine. They reported almost negative incidence of H. warreni i n a l l p l o t s except one which i s l o c a t e d near the edge of the stand. The surrounding f o r e s t i s composed of lodgepole pine w i t h a f a i r l y prominent i n t e r m i x t u r e of b l a c k spruce and aspen. L i g h t i n f e s t a t i o n s of H. warreni appear to be present at most p o i n t s around the burn periphery. A wide v a r i e t y of h a b i t a t s i s represented w i t h i n the burn, ranging from very dry to near bog c o n d i t i o n s ; pine t r e e s survive on a l l but extreme moist s i t e s . A r e p r e s e n t a t i v e sample of f l o r a l species growing on average s i t e c o n ditions - 19 -were i d e n t i f i e d . An estimate of the r e l a t i v e abundance of each species i s given; the categories used were the same as for plants collected near plots 1 to 6 . In I965 three locations i n the Robb Burn were chosen at the periphery where a f a i r l y sharp boundary occurred between the young regeneration and the adjacent mature forest. Each location represented a different habitat type. These were i d e n t i f i e d as plot series VII, VIII and IX. Plot series VII was located on the south edge of the burn on a north facing gentle slope. The ground cover consisted of a 4 - 5 inch thickness of moss. F a i r l y moist conditions were a char a c t e r i s t i c feature. Plot series VIII and IX were located on l e v e l aspects on the north side of the burn. Duff depth was 1 -2 inches i n series VIII and 1 -3 inches i n series IX. Plot series VIII represented dry conditions while series IX was intermediate. ( i i ) Rocky Mountain House Study Area: Plot 10 (Strachan area) was located i n a stand of 95-100-year old pine with a scattered understory of black and white spruce;,. A description of t h i s stand by Crossley (1955) indicated that the number of pine stems per acre was 642 with an average diameter (d.b.h.) of 6 . 1 inches i n 1952. The 1966 study revealed 6 l 0 stems per acre and an average diameter of only 6 . 4 inches (d.b.h.). The stand appeared to be i n a general state of decadence as the crowns were very thi n and dead snags were evident i n most diameter classes. Regeneration Plot Series X: This stand was about 15 years old i n 1966 and originated from a f i r e i n about 19^3. I t s location i s 20 miles south of plot 10 . A mature pine forest of variable composition surrounds t h i s burn. Trees i n plot series X were sampled-in I966. A l l plots ( l to 10 and I to X) were used to determine weevil - 20 -population patterns of abundance, and to correlate weevil numbers with stand conditions. Plots 1 to 5 were followed intensively from 1961 to 1965 (except I964) to' establish patterns of population change with time, and i n r e l a t i o n to clearcutting. Plots 6 and 7 also served to show population change with time. The regeneration plots served to establish the age at which stands become i n i t i a l l y invaded, and to show the rate of subsequent weevil spread into the stand. 2 . 2 Design of Plots and Sampling Procedure 2 . 2 . 1 . Plots i n Mature Pine: P r i o r to 1961 a one-square mile area of land had been surveyed by s t a f f of the pulp company concerned into p a r a l l e l s t r i p s one-eighth mile wide. A clearcut pattern of pulpwood removal was late r carried out on alternate s t r i p s (Fig. 2 ) . Plots 1 to 5 were delineated p r i o r to any cutting i n such a manner that the surveyed l i n e s bisected each plot lengthwise. After tree removal the outline boundary divided each pl o t into clearcut and non-cut halves. Plot 6 was located outside the cutting area to permit weevil population sampling to be done independently of cutting. The boundaries of a l l plots remained fixed throughout the 1961 to 1965 sampling period. Plots 1 to 6 were each three acres i n area and were of equal dimensions (198 x 660 f t . ) . As shown i n the enlarged view of a pl o t i n Figure 2 , each was further subdivided into four equal longitudinal s t r i p s (designated A, B, C and D) and each s t r i p into four equal blocks. The block constituted a minimum-sized sampling area i n which 10 l i v i n g pine were randomly chosen using a table of random numbers. Two numbers were used to - 21 -locate each tree, one representing breadth,- the other length of the block i n average sized paces. The two values were paced o f f and the nearest tree from the point of intersection was tagged for subsequent examination. Each tree was considered the basic sampling unit from which a variety of observations and measurements were recorded. This included stem diameter and average duff depth around the tree base. Three measurements of duff depth were taken around each tree base and an average was calculated to the nearest inch. The root c o l l a r and root bases of each tree were thoroughly examined and a l l weevils found were recorded and removed from the tree. ' Their position upon the host, extent of damage and the stage of weevil development were also noted. A t o t a l of l 6 0 trees were examined i n each of plots 1 to 6 i n 1961. Immediately following t h i s sample a l l trees i n the A and B st r i p s of plots 1 to 5 were clearcut, while plot 6 remained undisturbed. In 1962 80 l i v i n g trees were sampled i n the C and D s t r i p s , while 80 cut stumps were examined i n the A and B s t r i p s of plots 1 to ' 5 . This procedure was repeated for the I963 sample. Plot 6 was sampled i n 1962 and i n I963 following the same ; . • procedure as i n 1961. A fourth sample was obtained i n the C and D st r i p s of plots 1 to 5 i n 1965 but only 200 trees were randomly selected for sampling. In th i s case 20 blocks were selected randomly from the t o t a l possible of kO with representation i n a l l C and D s t r i p s . Ten trees were examined i n each block. Plot 7 was delineated with the same dimensions as plots 1 to 6 and sampling was carried out i n 1962 and 1963. The method of tree location and sampling procedure was i d e n t i c a l to that i n plots 1 to 6 . During the I 9 6 I - I 9 6 5 sampling period no one tree was sampled more - 22 -than once. Each three-acre p l o t was s u f f i c i e n t l y l a rge to contain an estimated 40 -50 percent of unsampled trees at the end of the f o u r t h annual sample. The removal of w e evils from the sampled trees might be regarded as an i n t r o d u c t i o n of e r r o r to the sampling system by lowering the p o p u l a t i o n l e v e l f o r subsequent samples. However, t h i s was compensated somewhat by removing the d u f f l a y e r around each sampled t r e e to discourage immediate r e -a t t a c k , and thus impede f u r t h e r d i l u t i o n of the p o p u l a t i o n . Warren (l9??6b) described t h i s procedure as an e f f e c t i v e means of mechanical c o n t r o l of H y l o b i u s . The layout and sampling procedure i n p l o t s 8, 9 a n d 10 were t r e a t e d d i f f e r e n t l y from that described f o r p l o t s 1 to 7- I n p l o t 8 a t o t a l of 80 t r e e s were used. Fourty t r e e s were randomly chosen i n each of two seed blocks and the r e s u l t s were combined. P l o t s 9 a n d 10 were each o n e - f i f t h - a c r e c i r c u l a r p l o t s w i t h a r a d i a l dimension of 51.4 f t . The l o c a t i o n of each p l o t was s e l e c t e d as r e p r e s e n t i n g average s i t e c o n d i t i o n s . A l l l i v i n g pine w i t h i n each p l o t area were sampled. 2.2.2. P l o t s i n Regeneration Pine: P l o t s e r i e s I , I I , I I I and IV each co n s i s t e d of 15 one-mil-acre p l o t s (each was 6 . 6 x 6 . 6 f t . ) arranged s e r i a l l y without spacing. Each s e r i e s extended at r i g h t angles from a o u t l i n e boundary i n t o a c l e a r c u t area. The m i l - a c r e p l o t s were numbered c o n s e c u t i v e l y from the stand edge. A l l c o n i f e r seedlings i n the four p l o t s e r i e s were examined f o r evidence of w e e v i l damage i n 1963, and again i n I965 . Seedling ages and a r e p r e s e n t a t i v e sample of heights were measured i n 1965. The dimensions of p l o t VI measured 30 x 70 f t . A l l pine w i t h i n i t were measured f o r height and examined f o r weevils i n 1966. - 23 -Each of plot series VII, VIII, IX and X extended at rig h t angles from the peripheral edge of the stand into young regeneration pine. Each series consisted of 20-foot diameter c i r c u l a r plots spaced at 30-foot i n t e r v a l s . The number of plots established was 11, 8, 10 and 10 for series VII to X respectively. A l l trees within each c i r c u l a r plot were examined for the presence of weevils and i t s damage characteristics were noted. Trees were measured for height and diameter (d.s.h.) i n series VII, VIII and IX, and only heights were measured i n series X. Total counts of trees i n each c i r c u l a r plot provided a measure of density. 2 . 3 Techniques of Population Analysis: 2 . 3 . 1 . Treatment of Sample'Trees: Sampled trees i n plots 1 to 10 were r summarized by s t r i p and plot for each year using four s t a t i s t i c s . These were mean tree diameter (x), diameter range (R), standard deviation of diameters (s) and coeff i c i e n t of v a r i a t i o n of diameters (C.V.). The procedures of calculation were as outlined i n Steel and Torrie ( i 9 6 0 ) . The CV. values express sample standard deviation as a percentage of the sample mean and are therefore a r e l a t i v e measure of v a r i a t i o n . This s t a t i s t i c permits d i r e c t comparison between s t r i p s , plots, areas and years. 2 . 3 . 2 . Weevil Numbers and Population Structure: Weevil populations i n plots 1 to 10 were expressed i n two ways; as absolute numbers or numbers per block or per acre, and as numbers per tree. The l a t t e r expression i s a measure of population i n t e n s i t y and i s useful i n showing weevil-tree size relationships within and between stands. However, population i n t e n s i t y values may be affected by changes i n stand density and i n tree size. Weevil numbers on a fixed scale of measurement such as the block or acre allows r e l i a b l e comparisons - 24 -to be made between s i t e s , between stands and between years. Since only a portion of the trees were sampled i n plots 1 to 7 each year, weevil population estimates are based on counts of t o t a l numbers of trees per plot. Weevil numbers were compiled from t o t a l counts of l i v e larvae, pupae and tenerals removed from the r o o t - c o l l a r portion of the tree. Egg counts were excluded since they were ra r e l y observed i n the f i e l d , and i t was not always possible to distinguish l i v i n g from dead material. Mature adults were also excluded since they were few i n number, represented a non-stationary phase of the l i f e cycle and therefore, do not represent absolute values. The sampling period each year generally extended from May to early August. In plots 1 to 6, sampling began with plot 1 and progressed to plo t 6 each year. P l o t comparisons of weevil abundance were made using the s t a t i s t i c s : mean weevils per tree (x); range i n numbers found on sampled trees (R); standard deviation of weevils per tree (s) and the coefficient of va r i a t i o n of weevils per tree (C.V.). The structure of weevil populations i n plots 1 to 10 has been described i n a variety of ways. The percentage of larvae pupating each year served to estimate the proportion of the population transforming to new adults. Larval head capsules were measured dorsally at th e i r maximum width to determine the annual d i s t r i b u t i o n of size groups and ins t a r s . The frequency d i s t r i b u t i o n of weevil numbers per tree conformed to the negative binomial d i s t r i b u t i o n . Two parameters describe t h i s d i s t r i b u t i o n ; mean (x) and an exponent "k". As described by Southwood (1966) the "k" value provides a measure of the degree of dispersion i n a population, and i s a useful characteristic for comparing different populations of the same insect or populations from dif f e r e n t habitats and years, providing that a standard - 25 -sampling unit has been adhered to. The use of the tree as the basic sampling unit i n plots 1 to 10 was adequate for t h i s s t i p u l a t i o n . A l l "k" values of plots 1 to 10 were calculated by the i t e r a t i v e solution i n the following formula as outlined by Southwood (1966) . log JL = k log l _ t l n 0 k where N = numbers of trees sampled, n Q = number of trees with zero weevils, x = mean number of weevils per tree and "k"= measure of population dispersion. Populations of root weevils were further described using Taylor's power law. Taylor (1961) showed that when the mean (x) and variance (s ) of a series of samples are plotted they tend to increase together and to obey a power law as expressed by the following formula: 2 -b s = ax The parameters "a" and "b" are constants, where "a" i s largely a sampling factor and "b" i s said to represent a true "index of aggregation characteristic of and constant for the species (Southwood I966). In th i s respect i t describes an i n t r i n s i c property of H. warreni. To obtain estimates of these parameters plots 1 to 10 (except 9) were used. The plots were f i r s t divided into f i v e groups of i n f e s t a t i o n levels as given below. Group I had the highest i n f e s t a t i o n l e v e l , Group V had the lowest. Within each group, 15 sampled Group I: Plot 8 (1963) + plots 1 -5 CD (1965) Group I I : Plots 1 -5 ABCD (1961) + plots 1 -5 CD (1962) + plots 1 -5 CD (1963) Group I I I : Plot 6 (196I - I963) + plot 7 (1962-1963) - 26 -Group IV: P l o t 10 (1966) Group V: Plots 1 -5 AB (1963) trees were randomly drawn with replacement for each sample. Fifteen such samples were taken from each group, making a t o t a l of 75 samples. The mean (x) and variance (s ) were calculated for t o t a l weevil counts from each sample of 15 trees, and these values were then plotted on log-log paper. The constant "b" value may be used to establish an appropriate -transformation which, when applied to population values, establishes independence between variance and mean.(Southwood I966). The transformation i s determined by solving the following equation. P = 1•" 2 ° I f P•=. 0 , a log transformation should be used, and i f P = 0 . 5 , a square root transformation i s applicable. . 2 . 3 . 3 . Weevil D i s t r i b u t i o n Patterns i n the Forest and on the Host: A variety of methods was required to analyse weevil numbers i n r e l a t i o n to tree size, tree density and duff depth. In stands represented by plots 1 to 10 tree diameter classes of one-inch intervals were used; i n plots VII, VIII and IX diameters were taken to the nearest half-inch. Weevil numbers i n r e l a t i o n to tree size were analysed by s t r i p , year and by a r b i t r a r i l y defined population classes (Groups I to IV). Appropriate transformation scales were used i n order to subject the data to graphical and s t a t i s t i c a l presentation. Weevil numbers per tree were transformed to a log scale while a square root transformation was used for tree diameter. Because of low counts of weevils i n young stands the log of percentage trees attacked was used instead of weevil numbers. Straight l i n e s were f i t t e d to the transformed data by the least squares method of the weighted regression (Steel and Torrie i 9 6 0 ) . - 27 -This gave equal weight to the trees represented i n each diameter class. A t-t-est (LeClerg et,v a l . 1962) was applied to the correlation coeff i c i e n t (r) values i n each graph to test the n u l l hypothesis that r d i f f e r s s i g n i f i c a n t l y from zero. The I96I data from plots 1 to 6 were used to analyse weevil numbers i n r e l a t i o n to tree density. Total weevils per block area were estimated from t o t a l tree counts and from the 10 sampled trees i n each block. Each block was O.1875 acres. Tree attack incidence was used to describe the density relations i n young stands. Data from plots 1 to 7 were used to analyse weevil numbers i n r e l a t i o n to duff depth around the. bases of k, 8, .10'-and 12 inch diameter trees. Weevils found on main l a t e r a l roots were recorded separately from those found on the c o l l a r region. The two t a l l i e s were compared with respect to duff depths of different tree diameter groups. Numbers of weevils on roots and co l l a r regions were compared to determine whether the d i s t r i b u t i o n pattern of weevils remained constant on a l l host tree sizes. A l l l i v i n g trees sampled from 1961 to 1965 i n plots 1 to 5 were used -for t h i s analysis. The data were graphically presented and a straight l i n e was f i t t e d by the least squares method (LeClerg et:,- a l . 1962) . Weevil numbers i n plots VII, VIII and IX were related to different s i t e s ; each s i t e was characterized by a mean duff depth. 2 . 3 . ^ - . Weevil Attack Patterns: Several techniques were devised to describe weevil attack patterns i n young and old stands. Plot series I to X were established to determine the age when i n i t i a l weevil invasion occurs, the pattern of tree attack and the rate of weevil spread. In plots VI to X weevil attack patterns were determined with respect and VII to tree size d i s t r i b u t i o n s . Each of plot series I to IV Ato X commenced at a - 28 -outline boundary where an abrupt t r a n s i t i o n occurred between regeneration and mature pine. These areas provided the conditions necessary to follow the pattern of weevil emigration from the residual mature trees where "reservoir" populations existed. Percentage trees attacked were related to distance.from the stand edge. The patterns of current attacks i n young and old stands were analysed to establish a relationship between percentage of trees with current attacks and weevil numbers. This relationship was further explored as a sampling t o o l for survey purposes. The percentages of trees attacked, old and current attacks combined, i n a va r i e t y of young to old stands were broadly related to tree density and,s stand age. This was to establish the cumulative attack pattern during normal stand development. Trees i n the 65-70-year old stand near plots 1 to 5 were examined to determine the nature and history of attack since, the time of i n i t i a l invasion. Three groups of tree sizes were selected and these were designated Small, Medium and Large. Trees within each group were selected for uniformity of size and the weevil damage characteristics of each group were considered near average for the stand. A t o t a l of 31 tree stems were cut transversely at a l e v e l on the stump which was v i s u a l l y judged to represent the region of maximum weevil feeding damage (Fig. 3 ) . Each stump was smoothed with a rotary sander to c l a r i f y annual increment boundaries and old weevil scars. The l a t t e r were dated according to approximate year of attack and an estimate was made of the t o t a l number of attacks. These were t a l l i e d by consecutive five-year intervals for each stump, and then a series of averages were obtained for each of the three groups. In addition, r a d i a l growth measurements were taken at about the - 29 -F i g . 3- Cross-section through a 66-year old pine stump at root c o l l a r l e v e l where maximum damage was observed. Weevil scars are accentuated with black ink and numbers indicate approximate years of attack. Note large patch of dead phloem and cambial tissue which occurred at the age of 43-45 years. - 30 -10-inch stump l e v e l of each tree. Each series of measurements for each tree was i n turn an average of four sets of measurements taken at r i g h t angle transects upon the stump i n order to reduce the error r e s u l t i n g from asymmetrical growth. The values for a l l trees within each size group were then averaged to obtain one curve for each tree group. The frequency d i s t r i b u t i o n of weevil attacks for each tree group was summarized on the basis of numbers of scars per stump. 3 . Studies of the L i f e Stages of H. warreni B i o l o g i c a l factors i n d i s t r i b u t i o n and abundance were considered to concern microhabitat conditions for the larvae, pupae, adults and eggs, as w e l l as natural enemies of these stages. 3 . 1 . Larval Stage: Observations of larvae were made to determine the number of instars, pattern of gallery i n i t i a t i o n , feeding patterns and time of development, characteristics of bark i n the l a r v a l feeding universe and mortality factors. Larval instars were determined from head capsule width measurements recorded through a stereo microscope with a micrometer eyepiece. The d e f i n i t i o n of instars by capsule measurement was used i n i d e n t i f y i n g stages of development throughout the summer, i n rearing experiments and i n r e l a t i n g l a r v a l size to conditions within i t s feeding universe. Mature larvae extracted from pupal chambers were re a d i l y recognized as prepupae and measurements of the i r capsules served to. indicate range of size undergoing pupation. The s u r v i v a l of newly hatched larvae was tested i n a moist environment within a v i a l i n which no food was added. The larvae were - 31 -examined a f t e r f i v e days to determine t h e i r general c o n d i t i o n . Other f i r s t i n s t a r larvae were observed under experimental conditions to determine the manner of i n i t i a l excavation i n t o the bark t i s s u e , and t h e i r p a t t e r n of g a l l e r y formation. The larvae were placed upon f r e s h pine bark sec t i o n s kept moist i n p e t r i dishes. D a i l y observations were made f o r seven days when the l a r v a e were removed and t h e i r head capsules measured. The depth of feeding w i t h i n l i v e bark t i s s u e may be an important-aspect i n s u c c e s s f u l establishment and s u r v i v a l of young l a r v a e , and has i m p l i c a t i o n s i n making estimates of i t s damage p o t e n t i a l . This aspect of l a r v a l s i z e and feeding depth was examined on 20 -25-year o l d pine t r e e s . Bark s e c t i o n s c o n t a i n i n g the g a l l e r i e s of e a r l y i n s t a r l a r v a e were removed from t r e e s , and the average depth of p e n e t r a t i o n by each l a r v a was measured as w e l l as t o t a l bark t h i c k n e s s . Head capsule widths of the corresponding l a r v a e were recorded. Other observations were made of g a l l e r y o r i e n t a t i o n and feeding p a t t e r n s on young and o l d t r e e s . Measurement^ of the t o t a l g a l l e r y length scored through t o xylem t i s s u e of four mature l a r v a l wounds i n d i c a t e d the t o t a l amount of feeding r e q u i r e d per l a r v a , and was an estimate of the g i r d l i n g damage p o t e n t i a l . F i e l d observations of l a r v a l s i z e s and egg r e a r i n g s t u d i e s (Cerezke I967) provided i n f o r m a t i o n on the general r a t e and p e r i o d of l a r v a l development. Two aspects of bark morphology considered important to the w e l l being o f lar v a e were thi c k n e s s of l i v i n g phloem and the presence of r e s i n c a v i t i e s formed w i t h i n the phloem of the r o o t - c o l l a r zone. Bark thickness serves both n u t r i t i v e and p r o t e c t i v e r o l e s w h i l e r e s i n c a v i t i e s are at l e a s t p a r t l y p r o t e c t i v e . The d i s t r i b u t i o n of bark th i c k n e s s and the d i s t r i b u t i o n , - 32 -size and r e l a t i v e abundance of resin cavities were described on 20-25-year old pine trees. Three trees were selected from an ar.ea characterized with a moss covering of 3 - 5 inches. The trees were excavated intact and discs were cut from the main stem at two-inch intervals up to a height of 18 inches, thereafter at six-inch intervals to a height of four feet. The f i r s t ' d i s c was taken at the c o l l a r base. Discs were also removed, one from each of the main l a t e r a l roots at a distance of one inch from the stem axis. The bark thickness of each disc was obtained from an average of four measurements. Counts of the t o t a l number of bark r e s i n cavities were made from the'transverse cut of the bark on each disc; measurements were made using a micrometer eyepiece. The shape of the re s i n cavities varied from spherical to e l l i p s o i d a l and two measurements were taken of each cavity to derive an average value of the diameter. Thirty cavities were measured from each disc and the diameters were summed to obtain an o v e r a l l estimate of mean cavity diameter. This value was used to estimate the t o t a l cross-sectional area of the transverse bark section occupied by re s i n c a v i t i e s . The same procedure was applied to each disc. The t o t a l cross sectional area of the bark of each disc was calculated by treating the bark as a narrow rectangle since bark thickness and circumference can be measured d i r e c t l y . The length of the rectangle was an average of inside and outside bark circumference measurements. I t was recognized that, although the techniques for calculating r e s i n cavity s t a t i s t i c s had some inaccuracies, the data appeared adequate to show the general patterns. Bark thickness and resin cavity measurements were related to distance up the stem and on the l a t e r a l roots. Larval habitat temperatures were determined i n a clearcut area and i n an adjacent pine stand 65-70-years old. S o i l temperatures were - 33 -recorded at four cut stumps i n the open and at four tree "bases i n the forest using a potentiometer and thermocouple wires. The wires were inserted on the north and south aspects, and at two- and four-inch depths at each cut and non-cut stump. Readings were taken at two-hour intervals from 5:00 a.m. to 5:00 p.m. during an average sunny day i n July. For comparison, a i r temperatures were recorded at the same time i n t e r v a l s . S o i l temperature differences between cut and non-cut areas were related to pupae collections made i n the two habitats. 3 . 2 . Pupal Stage: Observations, were made of the microhabitat conditions of pupae within i t s chamber. These relate to the construction of the chamber, i t s placement with respect to the host tree and to duff surface and to orientation of the chamber. Data from sampling and rearing provided information on time of i n i t i a t i o n of the pupal stage and i t s duration. Because of th e i r f r a g i l i t y most pupae were reared i n moistened .vials after wrapping them i n d i v i d u a l l y i n soft tissue. 3 . 3 M o r t a l i t y Factors of a l l Stages: Natural mortality factors of a l l stages of the l i f e cycle'were observed during f i e l d collections i n a l l sample plots. These included i n t e r n a l and external parasites, predators, fungal disease and mortality due to other factors. 'When insect l a r v a l parasites were obtained an attempt was made to rear them through to adults. Samples of each unknown parasite and predator were submitted to taxonomic s p e c i a l i s t s for species i d e n t i f i c a t i o n . A c o l l e c t i o n of 46 shrews (Sorex cinereus cinereus . Kerr.) was made from p i t - f a l l traps located i n the region of plots 1 to 5 during 1963 and 1965. Their stomach contents were examined for s c l e r i t a l remains of the adult weevil. - 34 -3 - 4 . Adult and Egg Stages: Large numbers of adult weevils were required for behavior and f i e l d experimental studies. For this purpose a l l adults were obtained from the Robb area. Studies of the behavior of adults were • undertaken to i d e n t i f y and describe c r u c i a l periods during i t s d a i l y and seasonal existence i n the natural habitat. These periods can occur during adult dispersion i n the forest and during feeding, mating and oviposition. The timing and pattern of these events need to be described to interpret s u r v i v a l and population changes. Techniques were devised to describe: the d i s t r i b u t i o n of adults i n the forest i n r e l a t i o n to tree size; rate and d i r e c t i o n of adult dispersion; sequential changes i n adult a c t i v i t y or changes i n numbers during the summer period; longevity of adults; egg laying; mating and feeding. Experiments were conducted to describe adult a c t i v i t y hourly and d a i l y , and i n r e l a t i o n to l i g h t and temperature. Egg laying and mating a c t i v i t y were studied i n the f i e l d , i n the laboratory and from dissections of adults collected at intervals during the summer. 3 . 4 . 1 . Collecting Methods, Adult Numbers and Sex Ratios: The task of c o l l e c t i n g adults was tedious and time consuming. This d i f f i c u l t y was p a r t l y overcome with the adoption of several c o l l e c t i n g methods. V i r g i n adults were reared from pupae and tenerals collected within pupal chambers. Some mature adults were collected i n the duff at tree bases during the population sampling. A t h i r d method of c o l l e c t i o n was by trapping, which made use of the trap design i l l u s t r a t e d i n Figure 4 . The. trap i s a modification of a design used by Embree (1965) to c o l l e c t winter moths. I t consists of a half-gallon sized, wax-coated cardboard container with a two inch hole cut i n the bottom. The top rim of a paper cup was inverted over the hole inside the - 35 -ELASTIC BAND •TRANSPARENT PLASTIC • 1 / 2 - G A L L O N CONTAINER PAPER CUP • NYLON STOCKING - M E T A L LOOP •METAL STRIP Fig. k. Trap design used for l i v e trapping adult- H. warreni during mark-recapture -studies i n plots A, B, C and D. container and glued. The bottom of the cup was also removed. A portion of a nylon stocking was passed through the bottom of the container, through the inside of the cup and glued to i t s outside rim. The lower end of the nylon cone thus formed was fastened to a loop on'a metal s t r i p which passed around the tree trunk. The container was fixed to the tree with a small staple d i r e c t l y above the metal loop. Each metal s t r i p was cut 1-g- inches by k feet i n length from t h i n galvanized sheeting. The s t r i p was bent at ri g h t angles along i t s midlength to form a three-quarter inch flange when nailed around the tree trunk. The design of the trap took advantage of the entire tree circumference as a co l l e c t i n g surface, and of the adult habit of ascending trees during hours of darkness to feed i n the upper canopy (Reid 1952) . The adults were l i v e trapped as they ascended trees. The metal flange was oriented at an oblique angle with the stem axis to act as a guide i n directing the weevil to the nylon cone, and thence to the inside of the container. . A small pine branch t i p was placed at the bottom of the container as a food source and to attract the adult until.morning. The o r i g i n a l tops of the container were replaced with transparent p l a s t i c and fixed with an e l a s t i c band. This prevented escape of the weevils and prevented moisture from entering. In addition, the transparency appeared to be less disturbing to a weevil, entering the bottom of the container since i t did not shut out l i g h t from above. Sex r a t i o s of adults were determined from a variety of. adult co l l e c t i o n s . -These included l i v i n g and dead adults collected at tree bases, from pupal rearings and from traps located within plot areas. In I965 the trap method was tested on 60 trees, 30 were on boarder trees of a clearcut s t r i p and 30 were on trees approximately 50 feet within the same stand. Care - 37. -was taken to match the two trap tree groups by diameter size p r i o r to the setting of traps. In I966 traps were placed on an additional 43 trees at the border of a cut s t r i p and a l l captured adults were sexed. 3 . 4 . 2 . Dispersal Patterns of Adults: The patterns of t e r r e s t r i a l movement of adults were studied i n the 65-70-year old pine stand of plots 1 -5 using a capture-mafk-release-recapture technique. Two c i r c u l a r plots, each one-f i f t h of an acre and 105 feet i n diameter, were established as plots A and B (Fig. 2 ) . Plot A was established i n 1964; plot B i n the following year. Neither plot had physical boundaries so that dispersal movement to and from the plots was unrestricted. Collecting traps as described e a r l i e r were placed, one on each l i v i n g pine i n the two plots and these were checked each moaning.- A l l adults present were sexed and i n d i v i d u a l l y coded with "Glow-color" fluorescent paint of different colors. This paint was chosen for i t s fast-drying, long-lasting and low t o x i c i t y q u a l i t i e s , and i n addition, had good adhesive properties. The marking of individuals was carried out using a combination of one, two and three paint spots of the same color applied i n one, two or three of s i x different positions on the e l y t r a l surface. These positions were designated anterior, median and posterior on each elytron. This procedure permitted the i d e n t i f i c a t i o n of a t o t a l of 4 l Individuals with one color combination. A different color was used to segregate the sexes. The weevils were released at the same tree base after being marked. The position of each tree within the f i f t h - a c r e plots was measured to scale on large sheets of paper i n order that the path of subsequent recaptures of marked weevils could be plotted. The trapping system was not carried out continuously throughout the summer but at varying lengths, - 38- -ranging from four to 13 days i n June, July and August. Data were collected during 1964, 1965 and 1966 i n plot A and during 1965 and 1966 i n plot B. A similar trapping experiment was conducted i n 20-25-year old pine of the Robb Burn. During the f a l l of 1964 two c i r c u l a r plots, each 20 feet i n diameter were delineated side-by-side on a weevil-free s i t e . Each plot was enclosed with a six-inch plywood fence, on the inside surface of which a t h i n band of "Tree Tanglefoot" was applied. This material prevented the escape of the adults since they showed some repellency toward i t . Wo weevils were ever found stuck within i t . One application of the material each spring appeared to be adequate. The plot arenas were designated C and D and contained 47 trees with an average d.s.h. of 2 . 1 inches and 49 trees with an average d.s.h. of 2 . 1 inches respectively. The position of each tree was plotted to scale as i n plots A and B. F i f t y newly emerged adults (including 30 v i r g i n females and 20 males) were placed i n each arena during the f a l l of 1964 after each had been coded with paint for in d i v i d u a l recognition. Traps .were placed on 20 of the largest trees i n each plot i n the spring of 1965 and trapping was followed at intervals during the summers of I965 and 1966, as described for plots A and B. Fresh pine t i p s were added to the traps every few days. A hygrothermograph enclosed i n a Stevenson's screen was positioned immediately adjacent to plots C and D to record temperature and humidity at ground l e v e l . The data from the four plots were analyzed i n various ways. Absolute numbers of adults could not be determined i n plots A and B but r e l a t i v e numbers were obtained by the mark-recapture method. The weevils were expressed as mean numbers captured per day during three and four sequential periods of the summer. For plot and year comparisons adults were expressed as numbers of adult captures per day per trapping day. The mark-- 39 -recapture data from plots C and D were analysed s i m i l a r l y . The adults captured and recaptured during 196k, 1965 and 1966 i n plots A and B were analysed to describe rate of dispersion i n the forest. Linear distances between trap trees where the same weevils were captured, and the time i n number of days between recaptures were used as a measure of dispersion. These distances were measured from the scale drawings of plot areas. The average rate of linear t r a v e l during any one night by an adult was related to the average distance between trees, and to the average distance from each tree to i t s nearest neighbor. Average distance between trees was estimated by dividing the t o t a l area ( f t . ) by the number of trees. This estimate of the mean area occupied per tree was converted to a square, the length of the side of which provided a measure of the average distance between trees. In the case of nearest tree neighbor, the distance from each tree i n the plots to i t s nearest neighbor tree was measured and an average obtained for a l l trees. The data from plots A and B were analysed separately for d i r e c t i o n a l movement of adults. Only those trees were considered where the same i n d i v i d u a l weevil was recaptured on two consecutive mornings. In each case the tree with the f i r s t capture was considered as the o r i g i n and from i t the direction of the second tree was measured as a-deviation i'ndegrees from cardinal north. The observations were then t o t a l l e d into eight 45-degree quadrants. A chi square test was performed for a 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 r a t i o of males and females separately i n each p l o t . 3 . ^ . 3 . Weevil Reproduction: Several f i e l d and laboratory experiments were established for making observations on a variety of aspects of weevil reproduction. These studies are i d e n t i f i e d under separate experiments below. - 40 -Experiment 1: The pattern of oviposition was observed from tree base examinations i n plots C and D at the end of the summers of 1965 and 1966. Total larvae, t o t a l eggs and t h e i r positions on the host were observed. In order to test, the effect of duff depth upon egg laying behavior a layer of fresh sphagnum mosses was placed around each tree base i n plot C i n the spring of 1966 (Fig. 5 ) . The duff depth was thereby increased to 4 - 5 inches. Plot D remained as a control with no addition of moss, and had a duff thickness of 1 -2 inches. The number of eggs plus larvae per tree i n I966 was analysed with respect to tree diameter. The least squares method of a weighted regression was used to f i t l i n e s . Standard errors of the mean (S^) were calculated for t o t a l eggs and larvae collected i n each tree diameter class. Correlation coeff i c i e n t (r) values were computed for each pl o t . Experiment 2 : The patterns of oviposition and egg hatch were observed after paired adults were enclosed i n transparent p l a s t i c cups. These were inverted and held f i r m l y with wire on the outer iiark surface of tree bases. A l l cups were positioned immediately above the duff layer for ease of observation and were shaded from direct sunlight. A fresh pine branch t i p was supplied regularly as food. Twenty weevil pairs were thus prepared i n July, 1964 and were l e f t for a period of about three weeks. The cups were then removed and the pos i t i o n of each egg was marked with a pin. The eggs were checked for hatching throughout the f a l l of 1964 and again i n the spring of I965 . Experiment 3 : The fecundity and laying frequency were determined during the period from June 1 'to August 23 , 1964. Twenty-four pairs of adults - kl -F i g . 5- Circular-shaped plot C located i n the Robb Burn showing trap attachment to the main stems of the largest trees. Note layer of Sphagnum mosses placed around each tree base and a band of "Tree Tanglefoot" on the inside surface of the arena w a l l . - U2 -were enclosed i n paper cups inverted over fresh pine bark sections which were kept moist i n p e t r i dishes. The top of each cup was covered with screen mesh to prevent escape of the adults. This allowed the female minimal contact with the outer bark surface. A fresh pine branch t i p was added frequently as food. Daily checks were made of oviposition and a record was maintained of t o t a l eggs l a i d by each female. A l l eggs were transferred to moistened paper and stored i n p e t r i dishes for hatching. The average egg productivity was expressed as the number of eggs l a i d per female per day. Maximum fecundity per female during the t o t a l summer period was estimated by multiplying the average number of eggs l a i d per female per day by 103 days. This value of 103 was considered a reasonable estimate of the t o t a l egg laying period, extending from May 20 to August 3 1 . The p e r i o d i c i t y of oviposition was analysed by using the eggs l a i d i n 10-day intervals consecutively throughout the summer. For each 10-day period egg production was expressed as the average number of eggs l a i d per female per day. Experiment k: Egg v i a b i l i t y and period of embryonic development were studied from 39 paired weevils reared i n 70 ml. v i a l s during the summer of I965 . A small amount of moss with, a few drops of water added p e r i o d i c a l l y to each v i a l kept the environment moist. Fresh pine tips were added regularly as food. The v i a l s were stored i n a ventilated box submerged a few inches i n the ground within the Robb Burn. The rearing period extended from July 1 to the f i r s t week of September, and eggs were collected at about 10 -day i n t e r v a l s . These were transferred to sealed v i a l s , maintained i n an atmosphere saturated with moisture and stored i n the ventilated box u n t i l hatching was complete. The average period of embryonic development and - 43 -percentage hatch were calculated for each group of eggs from a 10-day period. Experiment 5: Some effects of temperature upon oviposition and early development of progeny were observed i n s p e c i a l l y constructed p l a s t i c cages (Cerezke 1967) . Thirty pairs of adults were enclosed, one pair per cage, during June, July and August of 1966. Two cages were fastened to a pine stump which sat In a pan of moist moss, and 15 pine stumps were thus prepared. Cages 1 to 10 were maintained at normal day-night l i g h t and temperature conditions. Cages 11 to 20 and 21 to 30 were stored i n cabinets maintained at constant 60° F and 50° F respectively. Temperature fluctuations i n each cabinet were of the order - 1.5° F. A l i g h t i n t e n s i t y of about four candle power was supplied to the two cabinets. The fluorescent l i g h t s were controlled with a timer to provide l i g h t during the hours from 5^00 a.m. to 8 : 3 0 p.m.; the remainder of the day was i n darkness. Weevil rearing was terminated after 50 days when the contents of a l l cages were ca r e f u l l y examined for numbers of eggs and larvae. The position of a l l eggs and larvae was noted. Egg productivity for each caged group of 10 females was expressed as numbers of eggs l a i d per female per day. Total counts of eggs included a l l larvae observed. Experiment 6: The development and gross changes i n the fat body and reproductive structures were observed from 36 dissected females collected at different periods during the summers of I964 and 1965. The f a t bodies and ovaries were given r e l a t i v e ratings of size; small, medium and large. The c r i t e r i a of ovary size was based upon counts of oocytes per four ovarioles present i n each female as follows: small = 12-24 oocytes; medium = 25 -36 oocytes and large = 36+ oocytes. Lengths of the germarium portions of - 44 -ovarioles were measured to determine changes i n size as a re s u l t of maturation. Also, lengths of spermathecal glands were measured to provide an index of mating and the egg laying condition. . Spermathecae were examined for the presence of spermatozoa and the vaginal pouch was checked for presence of spermatophores. These two characteristics helped to separate v i r g i n from mated females. 3.4.4. Light and Temperature Response and Orientation of Adults: A series of experiments were conducted to describe the d a i l y a c t i v i t y patterns of adult weevils within t h e i r natural habitat. A c t i v i t y was assessed i n r e l a t i o n to temperature, time of day and orientation within the forest. Experiment 1 : The influence of night temperatures upon weevil movement up tree stems was analysed from captured adults collected d a i l y i n the traps of plots C and D. Only the data collected during June, 1965 and 1966 were used. During the f i r s t stage of the analysis t o t a l d a i l y captures were correlated with temperatures recorded during the previous night at hourly intervals from 8 :00 p.m. u n t i l 1:00 a.m. A correlation coe f f i c i e n t value (r)^was calculated for each set of temperatures. These were plotted over time to indicate the hour of maximum correlation. The temperatures were extracted from hygrothermograph charts. In the second phase of analysis weevil numbers were plotted over temperatures recorded at t h i s r-maximum hour. A linea r regression was f i t t e d to the data. Experiment 2 : This experiment was established to observe the time of emergence of adult weevils from the duff during the evening, and the pattern of orientation above the duff surface. The experimental s i t e was i n a clearing of approximately one acre within the Robb Burn. A patch of ground - 45 -was smoothed near the- center of the c l e a r i n g and a small c i r c u l a r arena, 90 cm. i n diameter was constructed. Transparent acetate p l a s t i c , 1 0-mil i n thi c k n e s s and about 10 cm. high was used as the arena w a l l . A narrow band of "Tree Tanglefoot" was placed around the i n s i d e w a l l to discourage escape of a d u l t s . Ten-degree i n t e r v a l s were marked on the w a l l to f a c i l i t a t e the p l o t t i n g of a d u l t d i r e c t i o n a l movement. A s a p l i n g s i z e d pine t r e e and a post were p o s i t i o n e d u p r i g h t outside the arena at a distance of about two meters from the center of the arena. Weevils were placed i n the center of the arena and covered w i t h moss i n the e a r l y evening. Their time of appearance from the moss and path of movement were noted. Ground surface temperatures and l i g h t i n t e n s i t y were recorded at 15-minute i n t e r v a l s . Observations were made on June 15, 2 1 , 23, 27 and J u l y 6, 1966. The p a t t e r n of d i r e c t i o n a l movement was t a l l i e d i n t o 20-degree quadrants to determine whether the t r e e or post served as v i s u a l cues i n guidin g l a t e r a l movement over the f o r e s t f l o o r . Experiment 3« This experiment was conducted to observe behavior of male and female a d u l t s confined to a sm a l l arena. An o v a l shaped arena was constructed u s i n g plywood and Tree Tanglefoot as described p r e v i o u s l y , and enclosed two t r e e s In the 65 -70-year o l d stand. The smaller t r e e was four inches and the l a r g e r was 12 inches (d.s.h.). A s c a f f o l d was constructed around the tre e s to observe w e e v i l behavior up the tre e s to a height of 2 1 . 5 f e e t ( F i g . 6) where a r i n g of Tree Tanglefoot was placed around the main stem axes. Ten weevils of each sex were coded w i t h p a i n t and placed i n the arena on J u l y l 6 , I963 . Hourly checks were made f o r the next three days. General behavior p a t t e r n s were described f o r each sex. - k6 -F i g . 6. Arena and scaffold enclosing two pine trees i n the 65-70 year old stand used for adult weevil behavior studies. White markers on the tree stem measure one-foot intervals. - 1+7 -3.1+.5- A d u l t Feeding P a t t e r n Experiment 1: Two sm a l l arenas, s i x and seven f e e t i n diameter r e s p e c t i v e l y were constructed i n the Robb Burn to observe feeding behavior of a d u l t w e e v i l s . Each arena surrounded one co-dominant t r e e . A sm a l l number of ad u l t s was placed i n each arena and l e f t throughout the summer. Counts were made at the end of the summer of the. number of feeding scars on each branch at each internode l e v e l , and an average value was c a l c u l a t e d f o r each internode up the t r e e . The distance out on the branch from the main stem of each.feeding scar was a l s o measured and whether i t occurred on the upper or lower surfaces of the branch stock. . Experiment 2: Observations of adul t feeding were made on t e r m i n a l shoots o f 6-8-year o l d pine and on seedlings 1-2 inches high. I n the l a t t e r case four two-foot square arenas which enclosed s e v e r a l seedlings each were constructed. A few adult weevils were placed i n each arena and d a i l y checks were made of the seedlings f o r evidence of feeding. The experiment was terminated a f t e r two weeks. k. Studies of the E f f e c t s of Weevil Damage to Trees The main objective' o f these studies was to assess the impact of w e e v i l i n j u r y upon i t s host t r e e , and determine how the damage may e f f e c t the stand as a whole. L a r v a l feeding was considered to have an ( e f f e c t upon the host's defense mechanisms against f o r e i g n i n j u r y , upon t r e e m o r t a l i t y and growth r e d u c t i o n and upon changes i n stand s t r u c t u r e . These'effects i n t u r n have i m p l i c a t i o n s i n short and long term i n f l u e n c e s upon w e e v i l s u r v i v a l and abundance. The e f f e c t of weevils on trees was studi e d by measurements of shoots, - 48 -needles and ring increments. Observations were made of changes i n the r e s i n duct system and tracheid i n f i l t r a t i o n , and of wound repair patterns. h.l Anatomical E f f e c t s : The ro o t - c o l l a r zone of a variety of sizes and ages of pine were examined for effects of weevil damage. Cross-sections of main stems and of l a t e r a l roots and taproots were made adjacent to l a r v a l feeding s i t e s . The freshly cut sections were soaked i n 70 percent ethanol for a few days to f i x i n t r a c e l l u l a r starch and to dissolve excess r e s i n . V e r t i c a l r e s i n ducts were dif f e r e n t i a t e d with a starch-reacting stain of iodine, consisting of O.h gms. I + 1 . 8 gms. K l per 100 ml. water (Reid, personal communication). After they were dry the discs were sanded smooth with a rotary sander to c l a r i f y r i n g boundaries and old weevil scars. C e l l u l a r d e t a i l s i n the xylem were made more v i s i b l e with an application of several coats of a clear laquer such as "Urethane". Discs prepared i n t h i s manner could be examined, under magnification of at least 50 times. 4 . 2 . Growth Loss Effects: Some effects of weevil g i r d l i n g damage to trees were studied i n two young pine stands to estimate growth loss i n stem terminals, upper branch whorls, needles and of r a d i a l increment. Twenty pine trees i n the dominant to co-dominant category i n the Robb Burn stand and 21 similar sized trees seven miles south of Grande P r a i r i e (Fig. 1, area 3) were selected for growth measurements. The pine stand near Grande P r a i r i e was several acres i n extent, 20-25-years old and probably originated from f i r e and natural seeding. The area l i e s immediately outside the Lower F o o t h i l l s Section. In the two areas, 1 and 3 respectively (Fig. l ) , 10 and 11 trees were located which had current or very recent weevil damage amounting to about 50 percent g i r d l i n g of the root c o l l a r circumference. The remainder 10 trees i n each - h9 -area were selected as controls and had no attacks. Care was taken to locate these trees as near as possible to the attacked trees and having characteristics of size, crown shape and competitive aspects similar to the attacked group. The measurements were made during June and July, T965 i n the Robb Burn and i n September, I966 i n the stand near Grande P r a i r i e . A l l trees were excavated with most of the roots intact to allow careful examination of the root and c o l l a r regions for hidden weevil wounds. Tree age was determined at about the one-inch stump l e v e l . The extent of the c o l l a r girdled to xylem tissue on each attacked tree was accurately measured after a l l bark was removed from the root c o l l a r zone. This was expressed as a percentage of the inside bark circumference. The periods of weevil damage were dated from discs removed immediately above the l e v e l of wounding. The e a r l i e s t r i n g showing traumatic r e s i n duct formation was recorded as the year of i n i t i a l attack. An average year of attack was then calculated for each group of attacked trees. Terminal branch lengths of the 1963 and 1964 growths were measured on\trees from the Robb Burn. Also, the lengths of a l l 1964 l a t e r a l s of the top whorl and a l l 1963 l a t e r a l s of the second top whorl were measured. The lengths at each whorl were averaged for each tree and an o v e r a l l average was calculated for each tree group. In addition, 25 needles were removed from near mid-length of a l l 1964 and I963 l a t e r a l s ; t h e i r lengths were determined and an o v e r a l l average per year per tree group was calculated. Overall averages of the 1963 and I96U terminal lengths were s i m i l a r l y determined. On trees from the Grande P r a i r i e area measurements were made of the I966, I965 and 1964 terminal lengths, and of the I966, 1965 and I964 - 50 -l a t e r a l "branch lengths of the top, second-top and third-top whorls respectively. Their lengths were averaged s i m i l a r l y as i n the Robb Burn group. No measurements were made of needle lengths. The effects of weevil damage on stem growth increment- were analysed by using the three-dimensional growth patterns defined by Duff and Nolan (1953) for Pinus resinosa. The procedure used was similar to that of Mott et. a l . (1957) and Stark and Cook (1957) who applied the Duff and Nolan growth sequence patterns to the analysis of insect d e f o l i a t i o n damage on lodgepole pine, balsam f i r and eastern larch. For the terminology, d e f i n i t i o n and theory of the three growth measurement -sequences as they relate to insect-caused damage, the author refers to Graham (1963) . Only the essential characteristics of each sequence are given below. Type 1, or oblique sequence i s a series of ri n g thickness measurements taken at each internode from the top to the. base of each annual conical s h e l l of wood. The values i n each series of measurements c h a r a c t e r i s t i c a l l y r i s e to a maximum i n the f i r s t few internodes, then gradually decline toward t-he base of'the stem. The pattern i s claimed to be due to n u t r i t i o n a l gradients i n the stem. . The influence of e x t r i n s i c and i n t r i n s i c factors on growth may appear as a s h i f t i n the average l e v e l of l i n e which defines the inherent physiological gradient of values at the internodes. Type 2 , or horizontal sequence i s a series of measurements of ri n g widths i n a transverse section across a chosen internode. Increment values r i s e to•a maximum i n the f i r s t few rings and gradually decline towards the periphery i n a similar manner as i n the oblique sequence. The strong pattern - 51 -i n the f i r s t few rings i s derived from the type 1 sequence and i s also due to n u t r i t i o n a l gradients since each ring i s produced by progressively older cambia. Thus the decline towards the periphery, as w e l l as the systematic i n t r i n s i c variations, tend to mask the effects of random e x t r i n s i c factors. lype 3> or v e r t i c a l sequence i s a series of measurements made downward at successive internodes on rings produced by cambium of similar cambial age. I t i s thus free from effects of n u t r i t i o n a l gradient or cambium age and i s t h e o r e t i c a l l y the. best suited of the three sequences to portray the influence of e x t r i n s i c factors on r a d i a l growth i n different years. In preparing the trees for growth measurement sequences, discs of wood were removed near the lower t h i r d of at least the top 10 internodes of the axis and a bottom disc at the 10-inch stump l e v e l . Ring widths were measured i n four r a d i i at right angles on each disc and an average was calculated for each year's growth on each disc down the stem of each tree. Ring width measurements were made under a dissecting microscope to a tenth of a mm. For the oblique sequence measurements of the Robb Burn trees, f i v e annual increments were used; 1958, 1959> 1962, 1963 and 1964. The f i r s t two years represent the pre-attack period for most attacked trees while the l a s t three increments represent the post-attack period of some trees. Attacked trees from the Grande P r a i r i e area were treated s i m i l a r l y ; i . e . , i960 and 1961 increments represent the pre-attack period for most trees while 1962, 1963, 1964, 1965 and 1966 increments cover the period during and after attack. A l l annual increments from the p i t h to the stem periphery at the 10-inch stump l e v e l were used for the horizontal sequence measurements. In - 52 -the v e r t i c a l sequence the second rin g from the p i t h was measured at each internode of a l l trees. For the f i n a l analysis the data for each group of 10 and 11 trees were grouped to give a combined average of each year's growth at each internode l e v e l . The data have been plotted separately according to attacked vs_. non-attacked tree groups, separately for each area and separately by growth sequence. RESULTS 1. D i s t r i b u t i o n of Hylobius Warreni The distr i b u t i o n s of H. warreni and H. p i n i c o l a i n western Canada and the United States are i l l u s t r a t e d i n Figure 7. They coincide approximately with the Boreal Forest Region. Although the patterns of the species overlap considerably the data indicate that H. p i n i c o l a occupies a more northerly pattern. Adults of H. warreni were found as far north as 50 miles beyond the northern Alberta boundary and i n the Cypress H i l l s i n the southeastern extremity of the province. Several isolated populations of H. warreni exist-on islands o f f coastal B r i t i s h Columbia and southern Alaska, as w e l l as i n the Cypress H i l l s . No collections of either species have been reported south of the Alberta and B r i t i s h Columbia boundaries. The known d i s t r i b u t i o n of H. warreni i n Alberta i s indicated i n Figure 8 . Although the northern half of the province has not been adequately covered by surveys, most adult collections were from lodgepole pine forests along the f o o t h i l l s of the Rocky Mountains. Within the range of lodgepole F i g . 7 . Known d i s t r i b u t i o n of Hylobius warreni and H. p i n i c o l a i n western Canada and Alaska. Points i n B r i t i s h Columbia and the Yukon Territory were taken from Grant (1966) . F i g . 8 . Map of Alberta showing the d i s t r i b u t i o n of H. warreni i n r e l a t i o n to the Lower F o o t h i l l s Section. - 55 -pine g r e a t e s t c o n t i n u i t y o f the w e e v i l occurs i n the Lower F o o t h i l l s S e c t i o n , occupying an area roughly between Calgary and north of Grande P r a i r i e . C o l l e c t i o n s o f the a d u l t were a l s o obtained i n r e s t r i c t e d l o c a l i t i e s at v a l l e y bottoms i n Jasper, Yoho and Kootenay N a t i o n a l Parks. No c o l l e c t i o n s or evidence of damage were observed i n f o r e s t e d areas south of Calgary. Throughout A l b e r t a c o l l e c t i o n p o i n t s of H. warreni have ranged i n a l t i t u d e from 700 f e e t some 20 miles south of Lake Athabasca to near 5000 f e e t 40 miles west of Calgary. Along the f o o t h i l l s , w i t h i n the range of lodgepole pine, c o l l e c t i o n p o i n t s v a r i e d from 5000 f e e t west of Calgary to about 2500 f e e t i n the Peace R i v e r d i s t r i c t . . The d i s t r i b u t i o n p a t t e r n s of H. warreni and H. p i n i c o l a have been prepared from a d u l t c o l l e c t i o n s , but the host species i n v o l v e d have not always been a v a l i d i n d i c a t o r o f the p r e f e r r e d hosts. This i s t r u e except where l a r v a l feeding has been a s s o c i a t e d w i t h the c o l l e c t i o n . For example, i n A l b e r t a mature a d u l t s of H. warreni and H. p i n i c o l a have been removed from a Populus species and a S a l i x species r e s p e c t i v e l y . • No adult H. p i n i c o l a specimens were found i n the study areas of lodgepole pine. 2. General C h a r a c t e r i s t i c s of the Weevil H a b i t a t The d i s t r i b u t i o n of t r e e stem frequencies of p l o t s 1 to 5 i s described i n Figure 9? t r e e diameters v a r i e d from 3 to 16 inches (d.s.h.). Other stand s t a t i s t i c s measured i n 1965 are summarized below. Mean t r e e diameter (d.s.h.) 9 - 0 i n s . Average age 67 years Average height 60 f t . Average d e n s i t y 48l t r e e s per acre - 56 -1 6 0 -1 4 0 -1 2 0 -3 4 5 6 7 8 9 10 II 12 13 14 15 16 T R E E D I A M E T E R D I S T R I B U T I O N IN INS. (D.S.H.) Fig. 9 - Tree diameter frequency d i s t r i b u t i o n of sampled trees i n plots 1 to 5 during I961 . . The number of trees used was 800. - 57 -The s o i l p r o f i l e of the region of plots 1 to 5 can be described as a Textural Podzol which i s considered as an intergrade between the Podzol and the Grey Wooded S o i l Groups. Horizon descriptions are summarized as follows. L - H : \ - 1 inch; decomposing organic layer consisting of decaying pine needles, twig and l i t t e r of alder and other ground f l o r a l species; • " mostly black i n color; abundant mycelia present; l i n e of demarcation between L-H and Ae f a i r l y sharp. Ae : 1 - 1-g- inches; medium greyish yellow-red yellow (10 YR 5/2); generally strongly eluviated; fine sandy-clay-loam; fine granular, loose and structureless to weakly'platy; f r i a b l e ; t h i n AeB sometimes present or Ae may be weakly defined. Bft : 3 - 4 inches; f a i r l y dark yellow-red-yellow (10 YR 4/4); layer i s enriched with hydrated iron, some organic matter and s i l i c a t e clay; silty-clay-loam to very fine sandy-clay-loam; fine granular to weakly blocky, sometimes platy; f r i a b l e ; few traces of carbon; gleying generally present with mottles often prominent i n the lower B horizon. BtfC : 8-12 inches; medium dark reddish yellow (2.5 Y5A); a layer of variable thickness gradually intergrading into the C horizon; fine sandy clay; fine granular, weakly blocky to fragmental and weakly platy; f r i a b l e to firm; gleying generally present; stones of variable size scattered throughout the B horizon. C : Begins 12 - 18 inches down; medium dark reddish yellow (2.5 Y 5/4) ; fine sandy to sandy clay; fine granular, fragmental to weakly blocky; firm; scattered stoniness throughout; gleying and mottling present. - 58 -TABLE I. LIST OF GROUND FLORAL SPECIES REPRESENTATIVE OF THE 65 - 70-YEAR OLD PINE STAND OF PLOTS 1 TO 5 . Species , Relative Species Relative abundance abundance Mosses C a l l i e r g o n e l l a schreberi V.A. V i o l a (nephrophila ?) c . Brachythecium sp. C. Aster conspicuus F.C. Hylocomium splendens C. Lycopodium annotinum F.C. Hypnum crista-castrensis C M i t e l l a nuda F.C. Polytrichum commune - C. Equiseturn sylvaticum S. Bryum sp. F.C. Gymnocarpium dryopteris S. Ditrichum sp. F.C. Lycopodium obscurum S. Polytrichum juniperinum F.C. Mertensia paniculata S. Timmia austriaca F.C. Pyrola secunda S. Streptopus amplexifolius S. Herbs * A r a l i a nudicaulis C . Shrubs Arnica c o r d i f o l i a C. Calamagrostis canadensis C. Alnus crispa V.A. Cornus candensis C. Rosa a c i c u l a r i s C. Epilobium angustifolium C. Spiraea lucida C. Linnaea borealis . c . Viburnum edule C * Maianthemum canadense Rubus strigosus F.C. var. i n t e r i u s C. Vaccinium caespitosum F.C. Pyrola a s a r i f o l i a var. V. membranaceum F.C. a s a r i f o l i a C. Ledum groenlandicum S. Rubus pubescens C. Lonicera invoTucrata S. , Ribes lacustre S. * Vaccinium myrtilloides S. V.A. = very abundant; C. = common; F.C. = f a i r l y common; S. = scattered or scarce * Denotes key indicator plants of the Lower F o o t h i l l s Section. S c i e n t i f i c names of plant species are according to Conard (1956) and Moss (1959) -- 59 -TABLE I I . LIST OF GROUND FLORAL SPECIES REPRESENTATIVE OF AVERAGE SITE CONDITIONS IN THE ROBB BURN. Species Relative Species Relative abundance abundance Mosses and Lichens Fragaria v i r g i n i a n a var. glauca F.C. Polytrichum commune C. Equisetum scirpoides F.C. . Cladonia sp. F.C. Oryzopsis (pungens ?) F.C. Cladonia sp. F.C. V i o l a adunca F.C. Cladonia sp. F.C. Gentianella amarella P e l t i g e r a aphthosa F.C. ssp. acuta S. Pel t i g e r a canina F.C. Pedicularis labradorica S. Herbs Shrub s Antennaria neglecta C. Vaccinium v i t i s - i d e a e V..A. A. p a r v i f l o r a C. Arctostaphylos uva-ursi C. Cornus canadensis C. Rosa a c i c u l a r i s c . • Elymus innovatus C. Ledum groenlandicum F.C. Epilobium angustifolium C. Sa l i x sp. F.C. Linnaea borealis C. Betula pumila var. A c h i l l e a millefolium F.C. glandulifera S. Aster c i l i o l a t u s F.C. Shepherdia canadensis S. * Vaccinium myrtilloides S. V.A. = very abundant; C. = common; F.C. = f a i r l y common; S. = scattered or scarce. * Denotes key indicator plant of the Lower F o o t h i l l s Section. S c i e n t i f i c names of plant species are according to Conard (1956) and Moss (1959) . - 6o -A l i s t of ground f l o r a l species characteristic of the 65-70-year old stand of plots 1 to 5 i s given i n Table I. For comparison, Table I I shows the species representative of the Robb Burn. The r e l a t i v e abundance of each species i s expressed as one of four categories. Only seven species were common to the two pine stands; the r e l a t i v e abundance ratin g of these were i d e n t i c a l except for one species. Several species included i n Table I I , such as the lichens, Archtostaphylos uva-ursi and Antennaria spp. .are indicative of a dry habitat. Key indicator plants of the Lower F o o t h i l l s Section are indicated with an asterisk. The various plant canopy layers and th e i r approximate percentage cover of the forest floor i n the 65-70-year old stand are described i n Table I I I . Five d i s t i n c t canopy strata were recognized at 2 ins., k ins., 12 ins., TABLE I I I . VEGETATIONAL CANOPY STRATA OF FOUR SMALL PLOTS IN THE 65 - 70-YEAR OLD PINE STAND. Canopy layers Percentage ground Ave. height of dominant surface coverage . species forming d i s t i n c t canopy layers Moss species Herbs and low shrubs Cornus canadensis A r a l i a nudicaulis  Alnus crispa Pinus contorta var. l a t i f o l i a 82 65 15 2 inches k inches 12 inches 9 feet 60 feet - 61 -9 f t . and 60 f t . Forest floor levelness i n the 65-70-year old stand was found to undulate on the average of 5 .9 inches in-height every 4 . 7 feet horizontally. The main causes of t h i s appeared to be from tree uprooting and from decaying logs. The l a t t e r were abundant i n t h i s stand and most were covered with a growth of moss species. Decaying logs and p i t t i n g of the ground surface were far less abundant i n the Robb Burn. This reduction was p a r t l y the resu l t of a sanitation harvest of the burnt snags, and p a r t l y because the stand was largely 40-50-years old at the time of the burn. In contrast, the stump diameters of some standing snags i n the older stand were i n excess of .15 inches. 3 . Weevil Abundance, Their Change with Time and Attack Density The sampled trees of plots 1 to 5 are summarized i n Tables IV, V and VI, according to i n d i v i d u a l st r i p s A, B, C and D for each plot and year. Table VII summarizes the tree characteristics of plots 6 to 10. The coeffi c i e n t of v a r i a t i o n values of tree diameter range between 19 .4 and 3 4 . 6 percent. They indicate that the method of tree selection provided s u f f i c i e n t randomization. Tree density i n plots 1 to 5 varied from 356 to 525 trees per acre as calculated from s t r i p t o t a l s ; densities, i n plots 6, 7, 9 and 10 were considerably higher. Weevil numbers collected i n plots 1 to 5 are summarized i n Tables VIII, IX, and X, and i n Table XI for plots 6 to 10. The I965 data of plots 1 to 5 were combined for a l l C s t r i p s and a l l D s t r i p s (Table X i ) . In a l l cases the variance (s^) i s greater than the mean (x), indicating that the weevil populations were contagious. - 62 -TABLE IV. SUMMARY OF STAND DENSITY AND TREE DIAMETER (D.S.H.) CHARACTERISTICS IN H. WARRENI SAMPLING PLOTS 1 TO 5 DURING 1961. Plot _ and trees/acre N Y R S C.V. s t r i p P lot 1: A U-69 40 B 431 40 C 488 ho D 481 4o Plot 2: A 39^ 40 B 369. 40 C 356 40 D 363 ko Plot 3: A hl3 40 B 425 40 C 469 40 D 444 40 Plot 4: A 506 40 B 49U 40 C 506 40 D 444 40 Plot 5: A 525 40 B 500 40 C k9k 40 D 456 40 8.68 5-12 1.99 23.0 9-03 3-15 2 .88 31.9 8.08 4-11 1.93 23.9 8.55 4-14 2.39 27.9 9-93 6-15 2.13 21.5 9 .68 5-15 2.55 26.4 10.48 6-16 2.54 24 .3 9.58 4-16 2.69 2 8 . 1 8.80 3-1^ 2.61 29 .7 9.30 4-16 1.88 20.2 9 . 8 8 4-15 2. 5^ 26.2 8.80 lv-15 2.83 32.2 9-15 4-15 2.65 28.9 9 . 0 8 4 - i 4 2.79 30.7 8.63 4-14 2.38 27 .6 9-05 4-14 2.43 2 6 . 8 8.55 3-1^ 2.25 2 6 . 4 8.35 4-13 2 .3^ 2 8 . 0 8.45 4-14 2.44 2 8 . 9 8.73 k-13 2.57 29.5 N = number of trees sampled, Y = mean tree diameter per 40 sampled trees i n inches, R = range of tree diameter (s. h.) i n inches per 40 sampled trees, S = standard deviation of the diameters of 40 sampled trees, C.V. = coefficient of v a r i a t i o n of the diameters of 40 sampled trees. - 63 -TABLE V. SUMMARY OF TREE DIAMETER CHARACTERISTICS IN H. WARRENI SAMPLING PLOTS 1 TO 5 DURING I962. Plot and N Y R S C.V. s t r i p Plot 1: A 40 8.50 5-12 1.80 21.2 B 40 8.63 5-12 I . 9 6 22.7 C 40 8.63 4-12 2.34 27.1 D 40 8.55 4-14 2.79 ' 32.7 Plot 2: A 4o 9.18 5-13 1.78 19.4 B 4o 8.88 5-14 2.42 27-3 C 4o 9.98 5-15 2.82 28.2 D 4o 9.68 5-17 2.64 27.3 Plot 3: A 4o 8.78 4-15 2.59 29.5 B 4o 8.95 6-13 1.89 21.2 C 4o 8.68 4-14 2.69 31.0 D 4o 9.28 3-14 2.74 29.5 Plot 4: A 4o 8.48 3-16 2.28 26.9 B 4o 8.40 4-14 2.36 28.1 C 4o 9.28 6-13 1.95 21.0 D 4o 9.48 4-15 2.22 23.4 Plot 5: A 40 8.45 4-13 2.20 26.0 B 4o 8.73 4-12 1.91 21.9 C 4o 8.98 4-15 2.59 28.8 D 4o 8.73 5-13 2.39 27.4 N = number of trees sampled, Y = mean tree diameter per 40 sampled trees i n inches, R = range of tree diameter at stump height i n inches per 40 sampled trees, S = standard deviation-of the diameters of 40 sampled .trees, C.V. = coe f f i c i e n t of va r i a t i o n of the diameters of 40 sampled trees. - 64 -TABLE VI. SUMMARY OF TREE DIAMETER CHARACTERISTICS IN H. WARRENI SAMPLING PLOTS 1 TO 5 DURING I963. Plot and s t r i p N Y R S C.V. . Plot 1: A ko 8 . 3 4 -12 1.97 2 3 - 7 B ko 8 . 0 4 -12 2 .06 2 5 . 8 C ko 8 . 1 • 3-lk 2.66 32.9 D ko 9 . 0 4 - 1 5 2 .39 2 6 . 5 Plot 2 : A ko 8 . 1 4-12 2.12 2 6 . 2 B ko 8 . 3 ^ - 1 3 2 .42 29 .2 C ko 9 . 6 4-16 2.15 2 2 . 4 D ko 10.0 5-15 •2.24 2 2 . 4 Plot 3 : A ko 8 . 5 4 -12 2 .39 2 8 . 1 B ko 8 . 6 4 - 1 3 2 . 2 1 2 5 . 7 C ko 9 - 5 3 - 1 3 2 .12 2 2 . 4 D ko 9.h 4 - 1 6 2 .52 2 6 . 8 P l o t k: A ko 8 . 6 4-15 2 . 5 3 2 9 . 4 B ko. 8 . 8 5 -13 2 .27 2 5 . 8 C ko 9 . 5 5 -15 2 .45 2 5 . 8 D ko 9 - 3 k-13 2 .26 24 .3 Plot 5 : A ko 7 . 7 3 -12 2 .20 2 8 . 6 B ko 8.0 4 -12 2 .06 2 5 . 8 C ko 8 . 1 4 - 1 4 - 2 .80 3 ^ . 6 D ko 8 . 3 3 - 1 3 2 .55 3 0 . 8 N = number of trees sampled, Y = mean tree diameter per 40 sampled trees, i n inches, R = range of tree diameter at stump height per 40 sampled trees, S = standard deviation of the diameters of 40 sampled' trees, C.V. = coe f f i c i e n t of v a r i a t i o n of the diameters of 40 sampled trees. - 65 -TABLE V I I . CHARACTERISTICS OF TREES SAMPLED FOR H. WARRENI POPULATIONS IN SEVERAL PLOT AREAS OF MATURE PINE. P l o t and No. of year t r e e s / a c r e N R S C.V. Pt s . , 1-5: C, 1965 _ 100 8.69 3-15 2.49 28.6 P t s . . 1-5: D, 1965 - 100 8.73 5-15 2.35 27.0 P t . 6, 1961 595 160 8.07 3-14 2.17 26.9 P t . 6, 1962 - 160 8.28 3-15 2.33 28.1 P t . 6, 1963 - 160 7-79 3-14 2.12 27.2 P t . 7, 1962 545 160 8.58 5-14 1-95 22.7 P t . 7, 1963 - 160 8.46 4-15 2.09 24.7 P t . 8, 1963 - 80 10.52 5-15 2.39 22.7 P t . 9, 1966 640 128 7-50 3-12 2.22 29.6 P t . 10, 1966 610 122 7-50 4-12 1.81 24.1 N = number of trees sampled, Y = mean t r e e diameter i n inches, R =' range of t r e e diameter at stump heig ;ht i n inches, S = standard d e v i a t i o n of t r e e diameters C.V, . = c o e f f i c i e n t of v a r i a t i o n of tr e e diameters - 66 -TABLE V I I I . THE 1961 H. WARRENI POPULATIONS TALLIED BY STRIP IN PLOTS 1 TO 5. P l o t _ Number of and N X • R S C.V. • weevils s t r i p per acre Plot- 1: A 40 1.00 0-5 1.28 128 469 •B 76 1.90 0-10 3.67 193 819 C 70 1.75 0-8 2.23 127 853 D 45 1.13 0-6 1.84 164 541 P l o t 2: A 91 2.28 0-15 3-54 155 896 387 B 42 1.05 0-6 1.45 138 C 60 1.50 . 0-13 2.42 161 534 D 54 1.35 0-8 2.09 155 489 P l o t 3: A 56 1.40 0-8 1.93 138 578 B 98 ' 2.45 0-19 3.76 154 i o 4 i C 63 1.58 0-10 2.66 169 738 D 65 I .63 0-24 4.10 252 721 P l o t 4: A 80 2.00 0-9 2 .55 128 1013 B 74 I .85 0-10 2.73 148 913 C 41 1.03 0r8 1.87 183 519 D 97 2.43 0-17 3.63 150 1076 P l o t 5: A 40 1.00 0-9 1.83 183 525 B 64 1.60 0-10 2.38 149 800 C 76 1.90 0-8 2.18 249 938 D 65 1.63 0-10 2.39 147 741 N = number of weevils ( l a r v a e + pupae + t e n e r a l s ) , X = mean number of weevils per t r e e , R = range of number of weevils found on a l l sampled t r e e s , S = standard d e v i a t i o n of weevils per t r e e , C.V. = c o e f f i c i e n t of v a r i a t i o n of weevils per t r e e . - 67 -TABLE IX. THE I962 H. WARRENI POPULATIONS TALLIED BY STRIP IN PLOTS 1 TO 5. P l o t _ Number of and N X R S C.V. weevils s t r i p per acre Plot 1: A 66 1.65 0-7 2.23 135 773 B 67 1.68 0-12 2.55 152 722 C 91 2.28 0-14 3.06 135 1109 D 75 - 1.88 0-15 3.28 175 902 Plot 2: A 53 1.33 0-9 I.98 149 522 B 44 1.10 0-8 I.96 178 4o6 C 70 1.75 0-8 2.45 140 623 D 98 '2.45 0-14 3.hl 139 888 Plot 3: A 82 2.05 0-7 2.28 111 846 B 92 2.30 0-14 3.35 146 978 C 53 1.33 0-9 1.75 132 621 D 97 , 2.43 0-20 4.12 170 ' 1076 Plot 4: A 7^  I.85 0-13 2.98 161 937 B 40 1.00 0-7 1.75 175 k9h C 92- 2.30 0-15 3.5^  15^  1164 D 85 2.13 0-14 2.75 129 9^ 3 Plot 5: A 59 1.48 0-8 1.97 i3h 77^  B 70 1.75 0-11 2.70 15k 875 C 69 1.73 0-12 2.77 160 852 D 52 1.30 0-8 I.98 152 593 N = number of weevils (larvae + pupae + tenerals), X = mean number of weevils per tree, R = range of number of weevils found on a l l sampled trees, S = standard deviation of weevils per tree, C.V. = coeffic i e n t of v a r i a t i o n of weevils per tree. - 68 -TABLE X. THE I963 H. WARRENI POPULATIONS TALLIED BY STRIP IN PLOTS 1 TO 5. P l o t _ • Number of and N X R S ' C.V. weevils s t r i p per acre Plot 1 : A 12 0 .30 0 - 4 0 .94 313 141 B 17 0 . 4 3 0 - 3 0 . 8 1 191 183 C • 56 • 1.40 0 - 8 2 .15 153 683 D 100 2.50 0 - 1 1 2 . 9 1 116 1203 Plot 2 : A 17 0 . 4 3 o-4 0 . 9 3 219 167 B 15 0 . 3 8 o-4 0 . 8 7 231 138 C 77 1 .93 0 - 1 7 3 .50 182 686 D •90 2 .25 0 - 1 3 3 .23 143 816 Plot- 3 : A 19 0.48 0 - 3 0 .79 165 196 B 14 0.35 0 - 3 0 . 7 7 220 ' 149 C 88 2.20 0 -10 2 . 3 3 106 1031 D 63 1.58 0 - 7 3 .90 247 699 P l o t 4: A 24 0.60 0 - 4 0 . 9 8 164 304 B 19 0.48 0 - 5 0 . 9 3 196 235 C 86 2 .15 0 - 1 2 2 . 7 3 127 1088 D • 99 2.48 0 - 1 3 2 . 9 3 118 1098 P l o t 5: A 20 0 .50 0 - 3 0.8.5 • 170 263 B 14 0 . 3 5 0 - 3 0 .70 200 175 C 71 1.78 0 - 1 2 2 .57 145 876 D 74 1.85 0 - 1 5 3 . 0 1 163 844 N = number of weevils (larvae + pupae + tenerals), X = mean number of weevils per tree, R = range of number of weevils found on a l l sampled trees, S = standard deviation of weevils per tree, C.V. = coeffic i e n t of va r i a t i o n of weevils per tree. - 69 -TABLE XI. HYLOBIUS WARRENI POPULATIONS COLLECTED FROM SEVERAL PLOT AREAS OF MATURE PINE. Plot _ Number of and N X R S C.V. weevils year per acre Pts . 1 - 5 : C, 1965 381 3 . 8 l 0 - 2 9 5 .^3 L43 1764 Pts . 1 - 5 : D, 1965 255 - 2 .55 0 - 3 1 k.h2 173 1117 Pt. 6, 1961 153 0 . 9 6 0-14 1.97 206 569 Pt. 6, 1962 160 1.00 0 - 1 5 2 .16 216 595 Pt. 6, 1963 108 0 . 6 8 0 - 1 0 1 .5^ 228 402 Pt. 7, 1962 119 0 . 7 ^ 0 - 8 1.49 200 405 Pt. 7, 1963 110 0 . 6 9 0 - 1 7 1.68 244 375 Pt. 8, 1963 306 3.83 0 - 3 1 5.i+6 143 -Pt. 9, 1966 169 1.32 0 - 9 I . 9 8 150 845 Pt. 10, 1966 57 0 . 4 7 0 - 1 3 1.45 310 285 N = number of weevils (larvae + pupae + tenerals), X = mean number of weevils per tree, R = range of number of weevils found on a l l sampled trees, S = standard deviation of weevils per tree, C.V. = c o e f f i c i e n t of v a r i a t i o n of weevils per tree. - 70 -In plots 1 .to 5 most weevil population estimates f e l l into the range of 400 to 1000 weevils per acre. A substantial reduction i n numbers occurred i n the A and B s t r i p s i n 1963 as a r e s u l t of the clearcut treatment (Table X). There was wide v a r i a t i o n i n the numbers of weevils found on any one tree. The highest number recorded was 31 i n plots 1 to 5 (1965) and 31 i n plo t 8 . This v a r i a b i l i t y i s described by the C.V. values which range from 106 to 313 percent for a l l 10 p l o t s . In general the C.V. values are inversely related to weevil population estimates per acre (Tables VIII, IX, X and X l ) . Although weevil numbers were highly variable i t was possible to recognize di f f e r e n t levels of abundance between dif f e r e n t areas and stands. In Table XII the data from plots 1 to 10 (except 9) have been a r b i t r a r i l y divided into f i v e classes of abundance on the basis of average numbers of weevils per tree. The data show the pattern of change of infested tree frequencies with decreasing population densities. Changes i n the percentage of trees having no weevils are especially notable. The percentage of trees with one weevil were similar for a l l groups. The pattern of Group V i s not as c l e a r l y established as i n Groups I to IV. This may r e f l e c t the clearcut treatment applied to s t r i p s A and B. The weevil samples collected annually i n plots 1 to 7 were compared to show trends i n population density i n time. In plot 6 the values for weevils per tree (Table Xl) suggest a s l i g h t increase from 1961 to 1962, and a substantial reduction from I962 to I 9 6 3 . A similar trend occurred i n pl o t 7. Plots 1 to 5 showed an o v e r a l l yearly increase i n weevil density from 1961 to 1965 (Fig. 10, graphs C and D). Tables X I I I , XIV, XV and XVI show the structure of weevil populations - 71 -4 . 0 0 3 . 5 0 UJ 3 . 0 0 LU OL CC LU 2 . 5 0 a. > UJ 2 . 0 0 5 U. o CL UJ m 1.50 3 z IOO . 5 0 -J_ J 1961 1 9 6 2 1 9 6 3 YEARS 1 9 6 4 1 9 6 5 F i g . 10. Hylobius warreni p o p u l a t i o n l e v e l s i n d i f f e r e n t s t r i p s of p l o t s 1 to 5 during 196'1 to 1965. '• S t r i p s ' A and B were c l e a r c u t a f t e r the" 1961 sample was taken while s t r i p s C and-1) remained undisturbed. - 72 -TABLE X I I . COMPARISON OF SAMPLED TREE FREQUENCY DISTRIBUTIONS(IN PERCENT) BETWEEN PLOT GROUPS OF DIFFERENT WEEVIL INFESTATION LEVELS. Number of weevils Gr. I Gr. I I Gr. I l l Gr. IV Gr. V 0 32.14 46.63 67.50 77.87 73.25 1 17.86 16.63 15.00 12.30 17.00 2 12.86 .11.06 7.38 6.56 5-25 3 7.50 6.63 3.88 .82 3-00 4 3-93 5.25 1.88 - 1.25 5 6.79 4.88 . 1.13 .82 .25 6 3.21 2.44 1.13 .82 -7 1.43 1.88 .63 - -8 3.21 1.44 .50 - -9 1.43 .75 .38 -10 1.43 .63 .25 - -n 1.79 .31 - - -12 .71 • 50 - - -13 1.43 .25 - . .82 -14 •71 .19 .13 - -15 .36 .25 .13 - -16-20 1.07 .25 .13 . - -21-25 • 71 .06 - - -26-30 • 71 - - - -31-35 • 71 - - - -Group I : P l o t 8, 1963 + p l o t s 1-5 CD, 1965, Group I I : P l o t s 1-5 ABCD, 1961 + p l o t s 1-5 CD, 1962 + p l o t s 1-5 CD, I963, Group I I I : P l o t 6, 1961-1963 + p l o t 7, 1962-1963, Group IV: P l o t .10, 1966, Group V: P l o t s 1-5 AB, 1963. - 73 -TABLE X I I I . SUMMARY OF THE POPULATION STRUCTURE OF H. WARRENI COLLECTED IN PLOTS 1 TO 5 DURING 1961. Year L i f e Number of weevils Plots 1 .- 5 and stage Pt. 1 Pt. 2 Pt. 3 Pt. 4 Pt. 5 Total Total Percent s t r i p weevils pupal pupating c e l l s 1961 - A Larvae ko 90 55 77 37 299 ^5 14.7 Pupae 0 0 1 3 3 7 Tenerals 0 1 0 0 0 1 Adults 0 3 1 1 0 5 1961 - B Larvae 76 41 98 65 63 3^3 32 9 . 0 Pupae 0 0 0 9 2 11 Tenerals 0 1 0 0 0 1 Adults 0 6 3 6 2 17 1961 - C Larvae 70 60 63 38 73 30h 33 1 0 . 6 Pupae 0 0 0 3 3 6 Tenerals 0 0 0 0 0 0 Adults 1 5 1 2 1 10 1961 - D Larvae ^5 5h 65 88 58 310 40 1 2 . 3 Pupae 0 0 0 9 7 16 Tenerals 0 0 0 0 0 0 Adults 1 0 1 2 1 5 1961 - AB Larvae 116 131 153 142 :. ',2100 642 77 11 .6 Pupae 0 0 1 12 5 18 Tenerals 0 2 0 0 0 2 Adults 0 9 4 7 2 22 1961 -CD Larvae 115 114 128 126 131 614 73 1 1 . 5 Pupae 0 0 0 12 10 22 Tenerals 0 0 0 0 0 0 Adults 2 5 2 4 2 15 - 74 -TABLE XIV. SUMMARY OF THE POPULATION STRUCTURE.OF H. WARRENI COLLECTED IN PLOTS 1 TO 5 DURING 1962. Year L i f e Number of weevils Plots 1 - 5 and stage : : s t r i p Pt. 1 Pt. 2 Pt. 3 Pt. 4 Pt. 5 : Total Total Percent weevils pupal pupating c e l l s 1962 - A Larvae 66 53 81 74 57 331 56 1 6 . 8 Pupae 0 0 1 0 2 3 Tenerals 0 0 0 0 0 0 Adults 0 1 1 0 0 2 . 1962 - B Larvae .67 44 92 4o 66 309 70 22.4 Pupae 0 0 0 0 4 4 Tenerals 0 0 0 0 0 0 Adults 0 1 0 0 0 1 1962 - C Larvae 90 70 53 92 68 373 73 1 9 . 5 Pupae 0 0 0 0 l 1 Tenerals 1 ' 0 0 0 0 1 Adults 2 1 2 2 2 9 1962 - D Larvae 75 98 97 85 50 405 59 • 14 .5 Pupae 0 0 0 . 0 2 2 Tenerals 0 0 0 0 0 0 Adults 1 0 2 1 0 4 1962 -AB Larvae 133 97 173. 114 123 64o 126 19.5 Pupae 0 0 1 0 6 7 Tenerals 0 0 0 0 0 0 Adults 0 2 1 0 0 3 1962 - CD Larvae 165 168 150 177 118 778 132 I 6 . 9 Pupae 0 0 0 0 3 3 Tenerals 1 0 0 0 0 1 Adults 3 1 4 3 2 13 - 75 -TABLE XV. SUMMARY OF THE POPULATION STRUCTURE OF H. WARRENI COLLECTED IN PLOTS 1 TO 5 DURING 1963. Y e a r L i f e Number of weevils Plots 1 - 5 and stage : : s t r i p Pt. 1 Pt. 2 Pt. 3 Pt. 4 Pt. 5 Total Total Percent weevils pupal pupating c e l l s 1963 - A Larvae 11 15 19 13 3 61 60 65.2 Pupae 0 2 0 11 16 29 Tenerals 1 0 0 0 1 2 Adults 0 0 0 0 0 0 1963 - B Larvae 17 . 15 i 4 9 8 63 41 51.9 Pupae 0 0 0 10 6 16 Tenerals 0 0 0 0 0 0 Adults 0 0 0 0 0 • 0 1963 - C Larvae 56 77 88 • 81 58 360 ^9 1 3 - 0 Pupae 0 0 0 5 13. 18 Tenerals 0 0 0 0 0' 0 Adults 4 3 2 4 2 15 1963 - D Larvae 9 8 . 90 63 98 67 4 i 6 28 6 . 6 Pupae 0 0 0 1 7 8 Tenerals 2 0 . 0 0 0 2 Adults 2 2 1 1 3 9 1963 - AB Larvae 28 30 33 22 11 124 101 59.1 Pupae 0 2 0 21 22 h5 Tenerals 1 0 0 0 1 2 Adults 0 0 0 0 0 0 1963 - CD Larvae 15k 167 151 179 125 . 776 77 9 . 6 Pupae 0 0 0 6 20 26 Tenerals 2 0 0 • 0 0 2 Adults 6 5 3 5 5 24 - 76 -TABLE XVI. SUMMARY OF THE POPULATION STRUCTURE OF H. WARRENI COLLECTED IN SEVERAL PLOTS AND YEARS. L i f e stage Plots 1-5 Plot 6 Plot 7 Pt. 8 Pt. 9 Pt. 1( I965-C 1965-D 1961 1962 1963 1962 1963 1963 1966 1966 Larvae 357 237 137 153 106 120 110 291 15k 5^ Pupae 20 • 15 13 7 2 0 . 0 15 15 3 Tenerals 2 2 0 0 0 1 0 0 0 0 Adults 2 5 2 2 0 2 6 2 0 1 Total weevils 381 259 152 162 108 123 116 308 I69 58 Total pupal c e l l s 22 17 16 23 3 27 14 16 16 8 Percentage pupating 5 . 8 6 . 7 1 0 . 7 ik.h 2 . 8 2 2 . 3 12 .7 5.2 9 . 5 14.( - 77 -collected i n plots 1 to 10 during 1961 to 1966. Larvae of a l l sizes comprised the hulk of each population. Large v a r i a t i o n occurred between the numbers of pupae and tenerals recorded i n plots 1 to 5 during the same summer. Pupae did not appear u n t i l the second and t h i r d weeks of June. However, t h e i r chambers were e a s i l y recognized as early as mid-May. The percentage of the population pupating i n plots 1 to 5 was lowest i n I965 and highest i n 1962. The highest percentage i n plots 6 and 7 also occurred i n 1962. - Adult collections agreed with t h i s , being the highest i n 1963 for the C and D st r i p s of plots 1 to 5. The numbers of adults refer to those specimens which were found at tree bases during sampling. They ranged from zero to s i x for samples of 40 trees. Highest numbers of pupal c e l l s were reported i n plots 1 to 5, A and B, during I963 (Table XV); i . e . , 101 pupal c e l l s compared to 77 i n the C and D strip s of the same plots. The structure of the l a r v a l portion of the population from plots 1 to 5 and 9 are compared i n Figure 11 for the years 1 9 6 l , I962, 1963? I965 and 1966. Head capsule widths have been grouped into mm. categories. A l l d i s t r i b u t i o n curves show a similar pattern but the greatest v a r i a t i o n between samples occurred i n the early and late instars; the largest proportion being i n the late ins t a r s . When the i n d i v i d u a l tree i s used as the basic sampling unit for H.; warreni populations the frequency d i s t r i b u t i o n of numbers per tree (Table XII) appears to be adequately expressed by the negative binomial d i s t r i b u t i o n . Mean numbers of weevils per tree (x) and the corresponding "k" values are given for plots 1 to 10 (Table XVTl). The values of "k" vary from 0 .09 for the lowest population (except plots 1 to 5, AB, 1963) to 0 . 6 8 for the:ihighest. - 78 -11. Comparison of the structure of H. warreni l a r v a l populations between years for plots 1 to 5, 1961, 1962, 1963 and 1965 and plot 9 , 1966. - 79 -TABLE XVII. CALCULATED "K" VALUES OF THE NEGATIVE BINOMIAL DISTRIBUTION USED AS A MEASURE OF THE DEGREE OF AGGREGATION OF DIFFERENT WEEVIL POPULATIONS AND HABITATS. Plot descriptions N n 0 X k 1961, Pts. 1 - 5 : A 200 9I+ ' 1.53 0.42 B 200 90 1.78 0.43 C 200 102 1.55 0.33 D 200 104 I .63 0.30 1962, Pts. 1 - 5 : A 200 91 I .65 0.44 B 200 96 1.57 0.39 C 200 93 1.88 0.38 D 200 97 2.04 0.32 1963, Pts. 1- 5: A 200 144 0.46 0.14 B 200 150 o.ho 0.12 C 200 85 1.89 0.47 D 200 81 2.13 0.48 I965, Pts. 1 - 5: C 100 32 3-79 0.51 D 100 38 2.5^ 0.49 I961 , P l o t 6 160 103 ( 0.9k 0.19 1962, Plot 6 160 111 1.00 0.13 1963, Plot 6 160 113 0.68 0.15 1962, Plot 7 • 160 107 0.76 0.17 1963, Plot 7 160 106 0.69 0.18 1963, Plot 8 80 21 3.83 0.68 1966, Plot 9 • 128 71 1.32 0.28 1966, Plot 10 122 95 0.47 0.09 N = number of trees sampled, n 0 = number of trees with zero weevils, X = mean number of weevils per tree (based upon t o t a l larvae + pupae + tenerals), k = an index of aggregation or measure of dispersion i n the population - 8o -The populations of the weevil obtained i n a l l plots except 1 to 5, AB, 1963, are described i n Figure 12 according to Taylor's power law. For H. warreni the parameters "a" and "b" were estimated as 2.80 and I.92 respectively. When "p" i s determined from the following equation, i t has a value close to zero. p = 1 - |b This suggests that a logarithmic transformation should be applied to the raw sampled data for s t a t i s t i c a l evaluation. Data from sampling i n the regeneration plot series VII to X are summarized i n Table XVIII. In the plot series VII, VIII and IX the calculated tree densities varied from 1854 to 4687 stems per acre, but the pattern of tree attack, based upon a percentage of t o t a l trees, appeared to be nearly constant for the three different s i t e s ; i . e . , 13.7? 12.1 and 13.6 percent respectively. The percentage trees attacked i n series X was only 2.82, while the calculated density was 5391 stems per acre. The averages of numbers of weevils per tree were a l l considerably lower than observed i n plots 1 to .10. However, estimates of absolute numbers of weevils suggest a s i m i l a r i t y between the 20-25-year old stand and the 65-70-year old stand. The estimated population for plot series VII i s w e l l within the range of estimates for the older stands. The frequency distr i b u t i o n s of weevil attack density i n plot series VII to IX combined, and i n plot series X are shown i n Table XIX. Plots V and VI are added for comparison, although the values shown only indicate the number of trees with current attacks. Most attacked trees i n the two burn • areas each supported a weevil density of one per tree, and only one tree had three weevils. The tree heights of the infested trees of the burn and Fig. 12 . Variance plotted against the mean of H. warreni populations per 15 sampled trees, on a log-log scale to obtain the constant "a" and "b" values of Taylor's power law. Five different population levels and habitats are represented. The values beside the points indicate the number of points having the same coordinates. (Line sight-f i t t e d ) . -82.-TABLE XVIII. SUMMARY OF THE TREE AND WEEVIL MEASUREMENTS IN PINE STANDS IN THE ROBB AND RICINUS BURN AREAS. Pl o t No. Total Ave. Calcu-series plots trees tree lated sampled sampled density density per per plot acre Ave. Ave. % Ave.no. Estimated ht. diam. trees weevils popula-( f t . ) s.h. atta- per t i o n per (ins.) eked tree acre VII 11 327 3 3 . 8 4687 9 - 2 1 .5 13.7 0 . 1 2 1 567 VIII ' 8 107 1 3 . 4 1854 8 .2 1 .7 1 2 . 1 0 .047 87 IX 10 144 1 4 . 4 1996 1 0 . 4 2 .2 1 3 . 6 0.104 208 X 10 389 38.9 5391 6 . 4 - 2 . 8 0 .028 152 TABLE.XIX. SUMMARY OF TREE FREQUENCIES SHOWING WEEVIL DENSITY AND TREE SIZE CHARACTERISTICS. Robb Burn Ricinus Burn Plot series Plot series Plot V Pl o t VI VII, VIII, IX X No. of trees with: 1 weevil 2 weevils 3 weevils Ave. height of trees ( f t . ) with: 1 weevil 2 weevils 3 weevils 39 11 1 1 3 . 1 ( 2 . 5 ) * 1 2 . 3 (2 .2 ) 11 .5 ( 3 . 2 ) 7 2 0 9 . 0 11.0 5 - 5 6 . 1 * Denotes average tree diameter (d.s.h.) i n inches. - 83 -clearcut areas1 are not comparable because of the age differences between the stands. However, the data show that the largest stems i n each stand were preferred. k.. Relationship of Weevil Numbers With Stand Conditions 4 . 1 Relationship with Tree Size: Lodgepole pine i s c h a r a c t e r i s t i c a l l y a pioneer species and i s propagated, both by a r t i f i c i a l and natural means, i n e s s e n t i a l l y even-aged stands. A l l areas of plots 1 to 10 and I to.X followed th i s pattern even though tree sizes varied greatly within stands. Weevil numbers were l i n e a r l y related to tree size i n a l l stands analysed (Figs. 13 3 14, 15, l 6 , 17 and 18). The log transformation of weevil numbers per tree, plotted' over the square root transformation of tree diameters appears to provide the best o v e r a l l f i t of straight l i n e relationships for data i n Figs. 13 to 17 i n c l u s i v e . Large trees consistently supported more weevils than small trees. This pattern was e s s e n t i a l l y the same for s t r i p s A, B, C and D of plots 1 to 5 3 as w e l l as for different years of sampling. Clearcutting had the effect of decreasing the slope of the l i n e (Fig. 13, L4). A sharp increase i n weevil numbers was evident i n the C s t r i p s of the 1965 sample as compared to previous years (Fig. 1 5 ) . Similar graph patterns were evident for other mature stands where different levels of populations were recognized (Fig. 1 7 ) . Although actual insect numbers were not used i n the analysis of young stands a similar relationship as described above for mature stands was also evident i n the 20-25-year old stand of the Robb Burn (Fig. 1 8 ) . 4 . 2 Relationship with Tree Density: The estimated numbers of weevils per block i n plots 1 to 6 (1961 data) were analysed i n r e l a t i o n to tree density Figs. 13 and 14. Relationship between weevil numbers per tree .and tree diameter size for three d i f f e r e n t years i n st r i p s k and B of plots 1 to 5- Lines were- f i t t e d by least squares-method ' of the-weighted: regression-. ^ S i g n i f i c a n c e of r values'is at 0.01 pr o b a b i l i t y . - 84 -1961 A Y = . 4 4 6 5 X - I 0 4 2 4 r =.9227** x x 1962 A Y - . 5 0 0 2 X - I . I 8 3 2 r = . 9 4 3 3 * * o o 1963 A Y = 2 2 8 9 X - . 5 4 0 0 r = . 8 6 8 5 * * a . 1961 B Y - - . 5 0 0 2 X-1.1941 r = . 9 5 0 5 * * x x 1962 B Y = . 4 8 0 4 X - 1.1263 r = 9 2 4 9 * * o o 1963 B Y=.233!X-r= 8962 . 5 9 2 8 l — i — i — r ~ i — i \/TREE DIAMETER + I (INCHES) Figs. 15 and 16. Relationship between numbers of weevils per tree and tree diameter size for four d i f f e r e n t years i n st r i p s C and D of plots 1 to 5- Lines were f i t t e d by least squares method of the weighted regression. **Significance of r values i s at 0 . 0 1 p r o b a b i l i t y . - 85 -.50, 1.40 1.30 1.201 1.10 1.00 £ -90 I OL. UI Q-«« 8 0 | > - • 1961 C Y = 4 0 7 2 X - 0 . 9 1 0 6 r = 9 5 2 0 * * x x 1962 C ui =5 tr ui m o 7 0 .60 .50 .40 .30 .20 .10 Y = . 5 3 5 8 X - I 2 8 7 2 r = 9 5 8 0 * " * - o l 9 6 3 C Y= 3 5 4 8 X - 0 .6785 r = . 8 6 5 0 * * - » I 9 6 5 C Y = . 7 I I 2 X - 1.6442 r = . 8 8 9 2 * * • / / / • • 1961 D Y = . 4 4 6 8 X - 1 . 0 3 0 7 r = 8 8 7 5 * * x x 1962 D Y = . 6 4 8 I X - I . 6 4 3 9 r = 9 5 4 9 * * |_ o o|963 D Y = . 4 7 3 2 X - I 0 7 3 7 r = . 8 7 9 9 * * T v 1965 D Y = . 5 6 0 4 X - I . 2 7 2 0 r = . 8 2 7 2 * * / T R E E DIAMETER + I (INCHES) F i g . 17 . Relationship between numbers of weevils per tree and tree 'diameter size for four d i f f e r e n t levels of abundance. Group I includes plot 8 and plots 1 - 5, CD - 1965; Group I I includes plots 1 - 5 , ABCD -1961, CD - 1962 and CD - 1963; Group I I I includes plots 6 and 7, I96I - 1963; Group IV includes plot 10. Lines were f i t t e d by least squares method of a weighted regression. ^ S i g n i f i c a n c e of r values i s at 0 . 0 1 p r o b a b i l i t y . - 87 -Fig. 18. Relationship "between percent trees attacked (old and current attacks) and tree diameter i n the 20-25-year old stand of plots VII, VIII and IX. Line was f i t t e d by least squares method. ^ S i g n i f i c a n c e of r value i s at 0 .01 probability. - 88 -per block (Fig. 19). These data suggested that maximum population levels were attained at a density of between 80 and 95 stems per block, or i n the range 426 - 506 stems per acre. In general, low tree density plot areas had low numbers of weevils per acre, and s i m i l a r l y for high density areas. . A tree density relationship could not be c l e a r l y established i n the regeneration plots VII to X. Figures 20 and 21 provide an indication that the percentage trees attacked may be inversely related to tree density. However, the data are masked by the fact that percentage attacks i n these young stands are l i k e l y highest at the stand periphery. 4 . 3 Relationship with Duff Depth: The measurements of duff depth i n plots 1 to 10 indicated some v a r i a b i l i t y between sites (Table XX) but that differences between population levels on different sites were not necessarily related to duff thickness. _ The quality of duff material was also, highly variable and may re l a t e to weevil numbers. For example, a forest floor consisting largely of moss species did not appear to be as favorable for the weevil habitat ( i . e . , plots 6, 1 and 10) as a forest floor comprising a mixture of moss and herb species ( i . e . , plots 1 to 5 ) . Within each forest type the depth of duff material around each tree base bears a strong relationship to the pattern of weevil d i s t r i b u t i o n . Figures 22 and 23 describe weevil numbers per tree i n r e l a t i o n to duff depth for 4, 8, 10 and 12 inch diameter trees. Three patterns are apparent i n Figure 2 2 : ( l ) weevil numbers tend to increase with increasing duff depth, except i n the four inch diameter class; (2) weevil density increased with increasing tree size and (3) the r e l a t i v e steepness of the curves indicate that duff - 89 -Fig. 19. Relationship "between weevil numbers per block and tree density per block i n the 65-70-year old pine stand of plots 1 to 6. Numbers beside the dots indicate t o t a l trees. F i g . 20. Tree density and weevil series VII, VIII and IX distance from the stand attack pattern i n the regeneration plot combined, and plotted i n r e l a t i o n to periphery. F i g . 21. Tree density and weevil attack pattern i n plot X, plotted i n r e l a t i o n to distance from the stand periphery.-- 90 -3 0 6 0 9 0 1 2 0 1 5 0 1 8 0 2 1 0 2 4 0 2 7 0 3 0 0 DISTANCE FROM STAND EDGE (FT.) - 91 -7.0 r 3 4 5 6 7 DUFF DEPTH IN INCHES Fig. 22. Relationship between weevil numbers per tree and duff depth of four tree diameter classes i n plots 1 to 5-- 92 -TABLE XX. AVERAGE DUFF DEPTH IN INCHES MEASURED AT THE BASE OF SAMPLED TREES IN PLOTS 1 TO 10. Plot number 1 2 3 4 5 6 7 8 ' 9 10 Average duff 4 . 4 4.9 5 . 3 5 -5 5 .7 5 -6 4 . 4 3 . 6 5 -9 7 . 2 depth depth becomes increasingly important to weevil populations as tree size increases. Figure 23 includes data from plots 6 and 7 but only the second pattern of weevil abundance i s apparent. The data were further analysed to determine how the pattern of duff depth d i s t r i b u t i o n relates to the four tree diameter classes, and how th i s might affect weevil abundance. Figure 24 suggests that with, increasing tree diameter, there i s a proportionately larger percentage of trees with thicker duff material around t h e i r bases; trees of the four inch diameter class have the lowest percentage with thick duff while trees of the 12 inch class have the highest. The duff depth factor was analysed to determine i t s role i n defining the l i m i t s of the feeding and developmental zone of immature weevil stages on the host. Figures 25 and 26 show the pattern of weevil numbers i n r e l a t i o n to th e i r d i s t r i b u t i o n upon the host tree and to duff depth. The proportion of weevils found on the roots follows a similar pattern as weevils on the c o l l a r ; i . e., as tree size increases,. weevil attacks become more numerous on the main l a t e r a l roots. The c o l l a r region, however, supports the largest - 93 -DUFF DEPTH IN INCHES Fig. 23. Relationship between weevil numbers per tree and duff depth of four tree diameter classes i n plots 6 and 7. - 9h -55.0r Fig. 2k. Frequency distr i b u t i o n s of duff depth of four different tree diameter classes i n plots 1 to 5. - 95 -Fig. 25. Relationship of numbers of weevils per tree and duff depth with comparisons for three different tree diameter classes i n plots 1 to 5. - 96 -T R E E DIAM. GROUP 11,12,13 8, 9,10 4, 5, 6 C O L L A R ROOTS 4 5 6 DUFF DEPTH IN INCHES Fig. 26. Relationship of numbers of weevils per tree and duff depth with comparisons for three different tree diameter classes i n plots 6 and 7. - 97 -proportion of the population (Table XXI). Figure 27 provides evidence that the r a t i o of weevils on roots to c o l l a r increases d i r e c t l y as tree size. This suggests that within the same stand type at least, there i s greater u t i l i z a t i o n of l a t e r a l root surfaces for l a r v a l feeding on large trees as compared, to small trees. The data i n Table XXI suggest that the proportion of weevils found on root and c o l l a r areas may vary from year to year. Lower percentages of weevils on the c o l l a r generally occurred i n 1963 for plots 1 to 5, 6 and 7 as compared to other years.- A substantial reduction also occurred i n the cut-over s t r i p s of plots 1 to 5 i n 19&3 "but t h i s probably resulted from different influences operating i n the non-cut portions. 4.4. Relationship with Clear Cutting: The sampling i n the clearcut halves of plots 1 to 5 showed that some larvae survived i n the cut stumps one and two years after tree removal. A small reduction i n weevil numbers appeared l i k e l y i n the f i r s t year after cutting while a sharp reduction occurred between I962 and 1963 (Fig. 1 0 ) . Bet-ween 1961 and I963 an estimated 67 percent of weevils were unaccounted for and i t may be assumed that- t h i s value represents the approximate mortality from the 1961 population l e v e l i n the • A and B s t r i p s . The population.in these s t r i p s i n 1963 consisted mostly of mature larvae and pupae. The percentage pupation was 5 9 - 1 (Table XV). The maximum number of weevils found on any one tree i n the A and B st r i p s i n 1961, I962 and I963 was 19, 14 and 5 respectively, while i n the C and D str i p s the maximum numbers were 24, 20 and 17 for the same years. Several changes i n the weevil habitat were noted i n the cleared areas as a re s u l t of tree removal. Rapid drying of the bark and sapwood of - 98 -oc < _l _l o o z- 0.60 o CO _ J 0.50 > LUUJ 0.40 CO o \ 0.30 CO h-o o 0.20 DC z o 0.10 CO _ J > LU 0.00 LU CO* o z Y= 0.0418 + 0.0321 X r = 0 . 7 9 8 5 * * 6 7 8 9 10 II TREE DIAMETER (INS.) 12 13 14 Fig. 27. Graph showing the proportional change of weevil numbers on roots and c o l l a r with increasing tree size. The data were taken from plots 1 to 5- Line was f i t t e d by the least. squares method.. "^Significance of the " r " value i s at the 0 . 0 1 p r o b a b i l i t y l e v e l . - 99 -TABLE XXI. SUMMARY OF THE PERCENTAGE OF WEEVIL POPULATIONS FOUND ON THE ROOT AND COLLAR REGIONS OF SAMPLED TREES IN PLOTS 1 TO 10. Year Plots Percentage weevils on roots Percentage weevils on c o l l a r 1961 1 - 5 , AB 1 9 . 7 8 0 . 3 1 - 5 , CD 1 1 . 1 88 .9 1962 1 - 5 , AB 4 .9 9 5 . 1 1 - 5 , CD 1 1 . 2 8 8 . 8 1963 1 - 5 , AB 14 .1 85.9 1 - 5 , CD 2 8 . 3 7 1 . 7 I965 1 - 5 , CD 3 8 . 6 6 1 . 4 1961 6 1 1 . 0 89.O 1962 6 10 .9 8 9 . I 1963 6 37 .0 63.O 1962 7 5 .0 9 5 - 0 1963 7 2 2 . 7 7 7 - 3 1963 8 68 .0 32 .0 1966 9 32 .0 68 .0 1966 10 3 8 . 6 61 .4 - 100 -stumps followed immediately after cutting. Duff compaction occurred especially around tree bases during cutting, and ad d i t i o n a l l y when the cut trees were skidded with horses. A l l branches and tree tops lopped from the pulpwood stems were l e f t i n a scattered pattern. They provided some protection as shade to the cut stumps at least during the f i r s t year. A variety of phloem feeding insects, such as secondary bark beetles and wood borers invaded the stumps during the f i r s t summer after cutting, as w e l l as some wood-decaying organisms. However, the inner phloem retained i t s whitish appearance for several months after tree harvest. In the regions of l a r v a l wounds no fresh r e s i n flow was evident, and many of the g a l l e r i e s were enclosed i n hardened masses of r e s i n and bark mixture. The lack of a fresh r e s i n supply appeared to influence the position of pupal case construction since many pupae were found i n an upright position on the stump. The developmental time of larvae and pupae appeared to be altered i n the A and B s t r i p s . In 1962 and I963 the sampling data suggested that pupae appeared e a r l i e r i n the A and B s t r i p s as compared to the C and D s t r i p s . For example, i n the clearcut area the f i r s t dates of pupa collections were June 12 and June 11 for I962 and I963 respectively. In the non-cut area for the same years the f i r s t dates of c o l l e c t i o n were July 19 and July 9-"+•5. Relationship with Stand Maturity: Differences i n measures of weevil population i n t e n s i t y and i n absolute numbers were evident i n young and old stands of pine. In the 15-year old stand of plot series X the maximum number of weevils found on any one tree was two while three was the maximum number found on trees i n the 20-25-year old stand (plot series VII, VIII and IX). Higher numbers were characteristic of a l l the older stands sampled i n plots - 101 -1 to 5, 6, 7 and 10 where 31 , 15, 17 and 13 weevils respectively were maximum numbers found on any one tree. • Estimates of absolute numbers i n plot series X, VII, VIII and IX were 152, 567, 87 and 208 weevils per acre i n that order. In contrast, estimates varied from 285 to 1764 weevils per acre i n plots 1 to 10. On this scale of measurement considerable overlap i n numbers existed between young and old stands. Higher estimates of weevil numbers than those given above for the young stands are possible on good growing s i t e s . 5. Patterns of Weevil Attack 5 . 1 . I n i t i a l Weevil Invasion into Regeneration Pine: The results of the pine regeneration survey i n the mil-acre plot series I, I I , I I I and IV are summarized i n Table XXII. No H. warreni larvae or adults, nor evidence of the i r feeding was observed i n the four plots series during I963 and 1965. I t may be assumed that no immigration of weevils had taken place up to 1965 when the trees were 1 to 7 years old. At th i s age the mean height of seedlings varied from 6 . 0 to 8 . 5 inches. An examination of trees i n plots V and VI i n 1966 revealed that 5 and 9 trees respectively were freshly attacked with larvae. This accounted for f i v e percent of the t o t a l trees i n plot VI. The frequency d i s t r i b u t i o n of tree heights i n plot VI i s shown i n Figure 28 . A l l .attacked trees occurred i n the dominant and co-dominant classes. Trees i n this plot ranged i n age from 3 to 9 years. An estimate of the age for s u s c e p t i b i l i t y to attack i n thi s regeneration would be 6 to 8 years, or when the trees are k to 5 feet high and have a diameter of about one inch (d.s.h.). No measurement of absolute - 102 -TABLE XXII. PINE REGENERATION SURVEY ON CLEARCUT SITES IN THE ROBB STUDY AREA. Plot series Total pine seedlings 1963 1965 Ave. no. l i n g s / m i l 1963 seed--acre 1965 Age range' 1963 1965 Ave. ht. • (ins.) 'in'1965" • Proportion m i l -acres stocked J.963' ' 1965 I 1+1 1+9 2 . 7 3 3 .27 - ' 2 - 5 7 .0 • 11/15 10/15 I I ^9 . 56 3.27 3 -73 1-1+ 2 - 7 8 . 5 ' 9/15 10/15 I I I 122 106 8.13 " 7.07 1 -3 2 - 5 6 . 0 13/15 13/15 IV 278 293 18.53 19 .53 1-3 1-5 7 .0 1V15 . 1^/15 weevil numbers was made i n p l o t VI since the larvae were l e f t undisturbed. The frequency d i s t r i b u t i o n of.tree size and weevil infested trees for plot series X and VII to IX are described i n Figures 29 and 30 respectively. The pattern of tree selection appears i d e n t i c a l with that described for plot VI. A t a l l y of the infested trees from the Robb Burn showed that almost 70 percent were i n the dominant category, while i n the suppressed tree class the attacks were rare. 5 . 2 . Rate of Weevil Spread i n Young Pine Stands: The rate of advance of weevils into young stands i s described i n Figures 20,< and 21 for the two burn areas of plot series VII to IX and X. The percentage of trees attacked i n each 20-foot diameter plot i n the Robb Burn suggested that few or no attacks occurred beyond approximately k-00 feet from the stand periphery. The time of i n i t i a l invasion into this stand, as determined by scar dating, was about 1955. Allowing two years for l a r v a l development, 12 years i s a F i g . 2 8 . Frequency d i s t r i b u t i o n of tree heights of pine regeneration, 3 - 9 -year s old, i n plot VI showing the pattern of weevil attacked trees. F i g . 29 . Frequency d i s t r i b u t i o n of tree heights of young pine, 15-years old i n plot -series X (Ricinus Burn), showing the pattern of weevil attacked trees. - 103 -I 1 TOTAL TREES mmm ATTACKED TREES i i 1 3.0 4.0 5.0 6.0 TREE HEIGHT (FT.) ' 7.0 8.0 I I TOTAL TREES • • ATTACKED TREES Jl 1 1 n TREE HEIGHT (FT.) F i g . 30. Frequency d i s t r i b u t i o n of tree diameters of pine, 20-25-years old (Robb Burn) i n plots VII, VIII and IX, and showing the weevil-attacked tree pattern. 16 O r - 104 -1 4 0 -1 2 0 -I 1 TOTAL TREES mmm ATTACKED TREES 1 0 0 >-o z LU a LU cr 8 0 6 0 -4 0 -TREE DIAMETER IN INCHES (D.S.H.) - 105 -reasonable estimate of the stand age at i n i t i a l invasion. Since that period the weevils have advanced into the stand at a rate of about 35 feet per year. A similar calculation for plot series X suggested a rate of spread of 45 feet per year. These estimates of 3 5 - ^ 5 feet per year must be regarded as only approximate since weevils were found far beyond 400 feet of plot series VII, and therefore, other factors' which influence weevil s u r v i v a l and behavior must be taken into account. An estimate was made of the rate of advance into the pine regeneration of p l o t VI. This p l o t was established at least 210 feet from.the nearest residual seed block with mature trees. Since the young pine originated after the 1957-58 clearcut i t may be assumed that the adult weevil had traversed the 210 feet by at least the eighth year after cutting. However, plot series I to IV suggested that no weevils had entered the stands up to the f i f t h year after cutting. This would allow 2 - 3 years to traverse the 210 feet, or at a rate of 70+ feet per year. 5 . 3 - Weevil Attack Pattern i n Pine Stands: The pattern of old and current weevil attacks was analysed i n r e l a t i o n to tree diameter for three different plot areas (Fig. 31). Population levels were highest i n area 1 and lowest i n area 3- A l l trees with a stump diameter of 8 inches or more had 100 percent old attacks, and many of the trees i n the smallest size classes showed no evidence of previous attack. No f i e l d evidence was found to suggest that small trees provided more unfavorable conditions for l a r v a l s u r v i val than large trees. The percentage of trees showing current feeding damage was d i r e c t l y correlated with tree diameter. Areas with high population levels had a F i g . 31 . Comparison of old attack and fresh attack patterns i n r e l a t i o n to tree diameter i n dif f e r e n t pine stands. Area 1 includes plots 1 to 5, ABCD - I96I; CD-1962; CD-1963. Area 2 includes plots 6 and 7, I 9 6 I - 6 3 . Area 3 includes plot 10, 1966. - i o 6 -T R E E DIAMETER AT S H . (INS.) - 107 -greater percentage of trees with .old and fresh attacks as compared to areas of low population levels. This indicates that population levels' are p a r t l y a function of tree size and of the percentage of trees with fresh attacks. The relationship of population levels and percentage of trees with current attacks i s shown i n Figure 32 . For stands 60+ years old ( i . e . , plots 1 to 10) weevil numbers per tree are l i n e a r l y correlated with'percentage of trees having fresh attacks. Stands less than 60 years old ( i . e . , p lot series VII to X) may be s i m i l a r l y correlated but may have steeper slopes. Four di f f e r e n t population levels have .been a r b i t r a r i l y segregated (Fig. 32; Table XXIII) to show the pattern of fresh attacks. The relationship suggests a simple method of population assessment i n pine stands. The nature and pattern of weevil attack since the time of i t s i n i t i a l invasion i n a 65-70-year old stand i s described from scar dating i n Figure 33 and Table XXIV. Curves for three tree size classes (small, medium and large) show the pattern of attack for a period of about 50 years. An average of the three graphs provides a general picture for the stand. .The data indicate that weevil abundance was maintained at three levels with respect to the three size groups. A l l three tree groups appear to have been i n i t i a l l y attacked within an i n t e r v a l of about fiv e years; the large group f i r s t and the small group l a s t . The corresponding diameters at f i r s t attack were largest for the large group and least for the small group. Figure 33 suggests a characteristic pattern of weevil attack during stand development. For the f i r s t 15 years after i n i t i a l invasion the rate of attack r i s e s slowly. This stage i s followed by a period of rapid increase - 108 -to a maximum l e v e l when the stand attains an age of approximately 45 years; thereafter i t declines. TABLE XXIII. POPULATION INDICES FOR PINE STANDS 60+ YEARS OLD. Population Percentage of trees No. weevils l e v e l with current attacks per tree Low 0 - 33 -5 0 - 0 .80 Low-medium 3 3 . 5 - ^ 9 . 0 0 .80 - 1.50 Medium U9.0 - 62 .0 I . 5 0 - 2 .50 High 62.0 + 2.50 + TABLE XXIV. SUMMARY OF H. WARRENI ATTACK HISTORY IN A 65-70-YEAR OLD PINE STAND Tree Total Av. diam. Av. age Av. diam. No. scars groups trees at s.h. Av. age f i r s t f i r s t per examined i n in s . attack attack (ins.) stump Small 10 5 - 5 6 6 . 0 3 2 . 3 2 .75 6 . 3 Medium 11 8 .2 6 6 . 7 2 9 . 3 3 -07 10.7 Large 10 1 2 . 3 6 7 - 2 2 7 - 5 h.26 1 8 . 8 F i g . 32 . Relationship between weevil numbers per tree and percent trees with fresh attacks. Data for the older stands, 60+ years, were obtained from plots 1 to 10. The four population classes are arbitrary and are defined i n Table XXIII. Line was f i t t e d by the least squares method. Data for the younger stand was obtained from plots VII, V I I I , IX and X; the l i n e was sight f i t t e d . The factor xlOO was used to eliminate negative values. 1 0 L _ 20 30 40 P E R C E N T T R E E S WITH 50 F R E S H A T T A C K S I L 60 70 80 - 110 -5 . 0 0 r 1 9 1 2 - 1 9 1 7 - 1 9 2 2 - 1 9 2 7 - 1 9 3 2 - 1 9 3 7 - 1 9 4 2 - 1 9 4 7 - 1 9 5 2 - 1 9 5 7 -16 21 2 6 31 3 6 41 4 6 51 5 6 6! FIVE - YEAR INTERVALS AGE 16 21 26 31 36 41 46 51 56 61 F i g . 33- History of weevil attack frequency on small, medium and large trees, 65-70-years old, and located between plots 1 to 5. Each l i n e represents an average of 10, 11 and 10 trees for the small, medium and large groups respectively. - I l l -An analysis of the r a d i a l growth patterns of the three tree classes indicate that the trees were maintained i n thei r respective stand positions throughout most of their growth (Fig. 3*0 . The period of maximum attack was taken from Figure 33 . Although a s l i g h t reduction i n growth rate i s evident i n the small and medium groups during the period of maximum attack,, i t i s unsafe t c claim a causal relationship. • The accumulative pattern of -weevil attack i n naturally stocked pine stands i s summarized i n Figure 35- A combination.of young and old stands i s represented to indicate the possible changes expected during normal stand development. The age categories assigned are only approximate since the graph does not include a l l age classes and s i t e v a r i a b i l i t y within even-aged stands. In the model tree density i s seen as a horizontal component which decreases i n time as a resu l t of natural thinning processes. Weevil attacks represent a v e r t i c a l component which increase with decreasing stand density and with stand" age. 6. Studies of the L i f e Stages of H. warreni 6 . 1 . Larval Stage: 6 . 1 . 1 . Larval Instar Determination: The frequency distr i b u t i o n s of l a r v a l head capsule width measurements indicated that only the f i r s t three instars can be c l e a r l y defined (Fig. 3 6 ) . Instar determinations beyond the t h i r d are obscured by an overlap of sizes. The prepupal size, d i s t r i b u t i o n suggests that s i x instars are possible. 6.-l."S.-.. Feeding Pattern and Development of Larvae: F i r s t instar larvae were observed from May to September i n old pine stands. Rearings of the f i r s t - 112 -PERIOD OF MAXIMUM ATTACK V / / / LARGE MEDIUM 1 8 9 9 - 1 9 0 2 - 1 9 0 7 - 1 9 1 2 - 1 9 1 7 - 1 9 2 2 - 1 9 2 7 - 1 9 3 2 - 1 9 3 7 - 1 9 4 2 - 1 9 4 7 - 1951- 1 9 5 7 -1 9 0 1 1 9 0 6 1911 1 9 1 6 1921 1 9 2 6 1931 1 9 3 6 1 9 4 1 1 9 4 6 1931 1 9 5 6 1961 FIVE YEAR INTERVALS Fig. 3 ^ . Radial growth characteristics of small, medium and large weevil-attacked trees, 65-70-years old and located between plots 1 to 5. The period of maximum.attack was taken from Fig. 32. - 113 -1 f i— P 1 1 1 1 ^ - i 1 0 10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 TREE DENSITY Fig. 35. P i c t o r i a l model showing the progressive weevil attack pattern i n naturally stocked pine stands ranging i n age from a few years old to mature. Age divisions were a r b i t r a r i l y assigned. A l l areas sampled were converted to a common unit area equivalent to a 10 -foot radius c i r c l e . F i g . 36. Frequency d i s t r i b u t i o n of Hylobius warreni. l a r v a l head capsule width determinations. Larvae were collected from plots 1 - 5 , ABCD, 1961 (----) and from plots 1 - 5 , CD, 1962 ( — — ) ; the numbers of larvae measured were 1255 and 778 respectively. LARVAL INSTARS 6 r i n j j j i v PREPUPA SIZE DISTRIBUTION 1.40 1.80 2.20 2.60 3.00 3.40 HYLOBIUS WARRENI LARVAL HEAD CAPSULE WIDTHS (MM) - 115 -instar without food indicated that they were s t i l l active after f i v e days and no mortality occurred at t h i s time. This experiment demonstrated that a five-day period would be s u f f i c i e n t to allow the i r successful establishment i n the bark substrate. F i e l d observations showed that, following hatch, the young larvae may burrow a short distance into the phloem tissue and commence to mine small feeding g a l l e r i e s . The depth of feeding i s generally very shallow at f i r s t and gallery orientation appears to take no fixed d i r e c t i o n . Often the gallery remains very l o c a l i z e d u n t i l the second or t h i r d instar, thereafter i t may follow a more, d i r e c t i o n a l path. Throughout the feeding period fine p a r t i c l e s of chewed-off bark are mixed with fresh r e s i n to form a matrix which the larva molds into a protective covering. The resin-material lat e r c r y s t a l l i z e s and hardens to provide an effective b a r r i e r against most forms of predators and parasites, as w e l l as waterproof protection.. The resin-bark mixture of g a l l e r i e s i s generally pinkish-brown i n color when fresh and turns whitish when dry and hard. In an experimental si t u a t i o n f i r s t instar larvae became oriented beneath bark scales through a series of wriggling motions. Once under the scale they began to chew into the bark tissue. By the second day they were not v i s i b l e and small amounts of bark frass marked thei r entry holes. After seven days the larvae had developed to the second instar and had extended small g a l l e r i e s within the bark. Their depth- of feeding was greater than had been observed i n the f i e l d . A necessary requirement for larvae during i n i t i a l bark penetration appeared to be some form of support to i n i t i a t e chewing a c t i v i t y . A l l instars responded negatively i n the presence of l i g h t . Since they possess two anterior o c e l l i the larvae may sense the upper l i m i t s of i t s universe v i s u a l l y . - 116 -The relationship between l a r v a l size and depth of gallery penetration i n l i v i n g phloem of young pine i s shown i n Figure 37. The data suggest that feeding damage i s confined to >phloem tissue u n t i l the end of the t h i r d instar. Larger instars may penetrate into the cambial and occasionally into sapwood tissues. Comparative studies i n older pine were not undertaken but general observations suggested a similar behavior. Larval feeding was confined mostly to the zone of the root c o l l a r l y i n g between the surface mineral s o i l layer and the upper surface of the duff. This zone may be defined as the l a r v a l universe. Within t h i s zone the orientation of the gallery extends i n almost any d i r e c t i o n on the c o l l a r and root bases. In many cases, especially i n late instars, the gallery network appeared three-dimensional as a result of resinous accumulations. An estimate of the damage po t e n t i a l of mature larvae showed that the g a l l e r i e s scored through to xylem tissue averaged 24 cm. i n length by 0.7 cm. i n width. These g a l l e r i e s were rarel y u n i d i r e c t i o n a l and most damage resulted i n patches of dead cambial tissue (Fig. 3 8 ) . Some differences i n the feeding gallery of late instar larvae were observed between young and old trees. In 10-25-year old stands the g a l l e r i e s were often more circumferentially oriented around the c o l l a r than i n older and larger trees (Fig. 39)> a n d extention of the gallery onto the roots was less common. Also, penetration into the sapwood was generally more pronounced on the younger trees. Nearly a l l observed tree mortality attributed to l a r v a l g i r d l i n g occurred i n trees less than 30 years old. The t o t a l length of time for development of each instar was not established. However, second instar larvae were obtained at least seven days after hatch as noted e a r l i e r . I t can be assumed that young larvae should - 117 -1.00 1.20 1.40 1.60 I.SO 2.00 LARVAL HEAD CAPSULE WIDTH (MM.) 240 Fig. 37. Relationship between l a r v a l size and average feeding depth i n the bark tissue of 20-25-year old pine trees. F i g . 38. H. warreni l a r v a l feeding wounds on a 65-year old pine stump with bark removed to show dead cambial areas. Fig. 39. Fifteen-year old pine stump showing the circumferential pattern of l a r v a l feeding i n the root c o l l a r zone. - 118 -- 119 -reach' the second to fourth instars during the f i r s t summer of development. Larval development continues throughout the second summer when most of the feeding damage i s done. In the following spring growth i s terminated with the construction of a special chamber which serves for the prepupa, pupa and teneral stages. I t s construction i s evident by the middle of May but the prepupal stage does not begin u n t i l the early part of.June. During pupal eel "1.'. for.'mation the l a r v a l gallery i s usually extended a few cm. away from the tree base. The chamber i s formed at the end of the ga l l e r y within 2 -10 cm. from the duff surface. Rotting logs lying at the base of trees were a common medium for the termination of the gallery. At the completion of i t s construction the chamber measures 8 -10 mm. inside diameter and about 25 mm. long. I t has a w a l l thickness of 4-6 mm. The inside w a l l i s smoothed and the .chamber i s sealed o f f behind and i n front of the larva. Most chambers l i e i n a near horizontal plane with the head capsule facing away from the tree. Large temperature differences were observed i n the l a r v a l universe between cut and non-cut stumps (Fig. 4 0 ) . In the natural habitat (non-cut area) d a i l y temperatures may fluctuate between 49 and 63°F. during the summer, while temperatures i n the cut stumps may vary between 52 and 82 °F. L i t t l e or no difference occurred between north and south aspects of non-cut stumps for each depth l e v e l , but 2 - 5 degree differences were apparent between aspects of each l e v e l in-.the cut .area. The temperature differences between cut and non-cut areas l i k e l y accounted for the e a r l i e r appearance of pupae i n the cut area by influencing the rate of l a r v a l development (see dates of f i r s t pupal collections i n section 4 . 4 ) . - 120 -Fig 1+0 Comparison of weevil habitat temperatures at cut stumps and at non-cut stumps. N-2" = two inch depth on north aspect; S-2 -two inch depth on south aspect; etc. - 121 -6 . 1 . 3 - Bark Microhabitat Studies: Studies of the l a r v a l microhabitat on pine trees which took into account bark thickness and r e s i n pockets, showed that certain patterns were apparent i n the l a r v a l feeding universe of the ro o t - c o l l a r zone. Bark thickness was minimal on l a t e r a l roots and reached a maximum two inches above the root base (Fig. kl). This l e v e l of the stem coincided approximately with mid-duff layer. No change i n bark thickness was detected above 16 inches. Resin pocket" diameter was least i n l a t e r a l root bark and increased almost two-and-a-half times at a l e v e l of four inches on the main stem (Fig. 42) while r e s i n pocket area was least on l a t e r a l roots and increased almost f i v e - f o l d at a height of four inches up the stem (Fig. "+3). The number of 2 re s i n pockets per mm was also minimal on the l a t e r a l roots and reached a maximum about eight inches up the stem (Fig. kk). The values comparing area and numbers of re s i n pockets to bark cross-sectional area were small but most of the larger pockets occurred near mid-alignment circumferentially i n the l i v i n g phloem (Fig. 4 5 ) . Their effectiveness as a protective bar r i e r against damaging agents i s thereby enhanced. The pockets provide an immediate source of re s i n i n l i q u i d form and many were a mm. or more i n diameter. 6 . 1 . 4 . M o r t a l i t y Factors of Larvae, Pupae and Tenerals: In a l l weevil study areas sampled during 1961 to 1966 observations of l a r v a l mortality under natural conditions was r e l a t i v e l y rare (Table XXV). Of those recorded a common cause appeared to be from excess moisture i n the gallery. Most of the dead larvae were i n the f i r s t to t h i r d instars. Moisture from stem run-off can accumulate i n g a l l e r i e s and other cavities within the resinous matrix around attacked tree bases. F i g . 41. Relationship between re s i n pocket diameter and position on the l a t e r a l roots (l-root) and main stem. F i g . 4 2 . Relationship between numbers of bark resin pockets.per bark cross-sectional area and position on the l a t e r a l roots (l-root) and up the main stem. Fi g . 4 3 . Ratio of bark r e s i n pocket area to bark area on a transverse plane of l a t e r a l roots (l-root) and main stem. Fi g . 44. Relationship of bark thickness and position on the l a t e r a l roots ( l - r ) and main stem. - 123 -F i g . 1+5. Cross-sectional view of a disc cut four inches above the root c o l l a r on the main stem of a 21-year old pine showing bark r e s i n pockets. - 124 -TABLE XXV. SUMMARY OF THE MORTALITY INCIDENCE TO IMMATURE STAGES OF H. WARRENI IN PLOTS 1 TO 10. No. of % mortal- % mortal-Year Plot Stage of mortality para- i t y of i t y of • Larva Prepupa Pupa Teneral sites weevils t o t a l i n pupal population c e l l s 1961 1 - 5 , AB - - - - 0 0 0 1961 1 - 5 , CD - 1 . - - 0 1.4 0 .26 1962 1 - 5 , AB 2 1 - 6 0 5 . 3 1.37 1962 1-5, - CD - - 4 5 1 7 . 0 1 .26 1963 1 - 5 , AB 1 8 2 3 5 15.0 10.00 1963 1 - 5 , CD - 2 8 4 4 ' 18.9 2 .19 1965 1 - 5 , CD 1 2 17+1* 8 3 4 4 . 3 4 . 8 1 1961 6 1 - - 0 0 0 . 6 6 1962 6 - - - - 1 4 . 2 0.62 1963 6 - 1 - 2 0 50.0 2 . 7 0 1962 7 - 2 4 . 6 0 3 0 . 8 9 .02 1963 7 - - - 3 0 1 7 . 6 2 .65 1963 8 1 - 4 5 0 3 4 . 6 3 .16 1966 9 1 3+1* - l 0 2 2 . 7 3.14 1966 10 - - - 2 0 2 0 . 0 3 .39 * Denotes specimens covered with white: fungus. - 125 -Total mortality of newly hatched larvae could not be assessed because of the low incidence of eggs found i n the f i e l d . Of a t o t a l of l6 eggs found on mature trees the oviposition sit e s varied from within the outer bark to about 5 cm. from the bark surface. Some mortality i s l i k e l y during the period between egg hatch and establishment of the larva i n the phloem tissue, although no evidence of parasitism, predation or disease was observed i n f i r s t or i n later instars. Mortality was not observed to re s u l t from overwintering. Several mortality factors of the prepupal and pupal stages were recorded (Table XXV) and i d e n t i f i e d . Pupae appeared to be p a r t i c u l a r l y susceptible to moisture accumulated i n the i r chamber. In some instances, free water appeared to weaken the case structure, and moistened chambers rea d i l y took on a blackish appearance with the development of fungal mycelia. A dry environment had a similar detrimental effect on reared pupae. Body f l u i d was lo s t and the weevils s h r i v e l l e d and died. Collections of pupae and young adults s t i l l i n the chamber were made i n May and early June of each sampling year but in- no instance were these pupae found a l i v e . This suggested that pupae are unable to withstand overwintering conditions, whereas tenerals can. Several specimens of a Hymenopterous parasite were collected and reared from weevil pupal chambers. These were i d e n t i f i e d as Dolichomitus tuberculatus tuberculatus (Fourc.) (Fig. 46) and belong to the family Ichneumonidae. They were i d e n t i f i e d by Mr. G. S. Walley at the Entomology Research I n s t i t u t e i n Ottawa. The d i s t r i b u t i o n of the parasite may coincide with that of H. warreni since collections i n Alberta were made at Embarras (near Lake Athabasca), Robb, near Edson and 10 miles west of Ricinus. F i g . 46. Female adult of Dolichomitus tuberculatus tuberculatus (Fourc.) and the weevil pupal chamber containing the case from which the parasite emerged. Scale i n mm.. Fi g . 1+7. Two l i v e H. warreni pupae i n cases and one dead prepupa ( l e f t ) i n a pupal case with the l a r v a l parasite, Dolichomitus .tuberculatus  tuberculatus (Fourc.). XI. - 126 -- 127 -The l i f e c y c l e of t h i s ; p a r a s i t e was r e c o n s t r u c t e d from f i e l d observations as f o l l o w s . The- a d u l t emerges from about mid-June to mid-July and deposits an egg i n a pupal chamber co n t a i n i n g a weevil: i n the prepupal stage. The newly hatched p a r a s i t e l a r v a feeds e x t e r n a l l y on i t s host ( F i g . 47) and develops i n about two weeks to a mature l a r v a . At t h i s time i t has consumed the body contents of i t s host. P a r a s i t e s found i n l a t e J u l y and August were u s u a l l y enclosed i n a greyish-brown case w i t h i n the o l d w e e v i l chamber. Here they remain as larvae u n t i l the f o l l o w i n g s p r i n g . Development to the pupal stage commences soon a f t e r the f r o s t leaves the ground i n May. Both male and female a d u l t s were c o l l e c t e d i n the f i e l d although the l a t t e r were most common. The incidence of the p a r a s i t e may account f o r up to f i v e percent m o r t a l i t y of weevils i n the pupal c e l l (Table XXV), however, excess moisture appeared to be the: main m o r t a l i t y f a c t o r . The values shown i n Table XXV are probably conservative since some p l o t s were sampled too e a r l y i n the year to detect m o r t a l i t y of prepupae, pupae and t e n e r a l s . Two specimens of a second i n s e c t organism ( F i g . 48) causing w e e v i l m o r t a l i t y of the prepupa and pupa stages were i d e n t i f i e d as Dipteran l a r v a e belonging to the f a m i l y L a p h r i i n a e ( A s i l i d a e ) . .These were i d e n t i f i e d by Dr. J . R. Vockeroth at the Entomology Research I n s t i t u t e i n Ottawa. A few dead prepupae, pupae and young a d u l t s i n pupal c e l l s were found covered w i t h a white f u n g a l mass b e l i e v e d to be the entomogenous fu n g a l p a r a s i t e , Beauveria bassiana ( B a l s . - C r i v . ) V u i l l . This same organism was p o s i t i v e l y i d e n t i f i e d on a number of dead adu l t H. warreni, but i n e i t h e r case the degree of v i r u l e n c e was not e s t a b l i s h e d . - 128 -Fig. h8. Dipteran larva of the family Laphriinae (Asilidae) collected from the pupal chamber of H. warreni (X 2.5). - 129 -6.2. Pupal Stage: Under natural f i e l d conditions pupae f i r s t appeared "between the t h i r d week of June and the early part of July, while the peak of abundance occurred near mid-July. The prepupal and pupal stages combined may l a s t up to eight weeks i n the pupal chamber. Teneral adults were generally observed after mid-August and some vacated the chamber before the end of t h i s month. They do th i s by chewing through the d i s t a l end of the chamber. Most tenerals emerge i n the f a l l while some may overwinter i n the chamber and emerge i n May and early June. 6 . 3 - Adult and Egg Stages: 6 . 3 . 1 . Numbers of Adults and Sex Ratios: The numbers of adults collected by the different methods are summarized i n Table XXVI, along with the corresponding sex r a t i o s . Adults collected under ( l ) - a and -c consisted of dead specimens found at tree bases. Many of these may not represent mortality of the same year since they were i n different stages of deterioration. Only the abdomens were available for i d e n t i f i c a t i o n of some of these. Wide variations i n the sex r a t i o s were apparent from the adults collected.by the dif f e r e n t methods. There was less v a r i a t i o n between collections made by the same or similar sampling method. Reared adults from 214 f i e l d collected pupae suggested that:.females were somewhat more abundant than males (method 6). Using the tree base-duff search method on trees within stands, more females than males were obtained (methods 1-b and 1-d), while the converse was true for adults collected on trees bordering cut s t r i p s (method 2). Si m i l a r l y , more males than females were obtained on border trees as compared with within trees by the trap method (methods 3, 4 and 5 ) . The collections from plots A and B showed similar sex ra t i o s - 130 -TABLE XX'VI. NUMBERS OF ADULTS AND THE SEX RATIOS OF H. WARRENI COLLECTED BY DIFFERENT METHODS IN DIFFERENT YEARS IN THE 65-7O-YEAR OLD STAND. Method, of sampling and l o c a t i o n Year Number females of a d u l t s males t o t a l Sex r a t i o «/o* • ( l ) Tree base-duff search w i t h i n stand: (a) dead a d u l t s 1961 13 20 33 O .65 (b) l i v i n g a d u l t s 1961 32 28 60 1.14 (c) dead a d u l t s 1962 16 ' 11 27 1.45 (d) l i v i n g a d u l t s 1962 . 44 26 70 I . 6 9 (2) Tree base-duff search border of cut s t r i p : (a) l i v i n g a d u l t s 1965 30 65 95 0.46 (b) l i v i n g a d u l t s 1966 5 40 h5 0 . 1 3 (3) Traps on 60 t r e e s : (a) 30 traps on border I965 36 h7 83 0 .77 (b) 30 t r a p s 50 f t . w i t h i n 1965 27 26 53 1.05 (4) Traps on 43 t r e e s at 0.44 • border of cut s t r i p : 1966 21 4 8 ' 69 (5) Traps, i n p l o t s A and B: (a) Traps on 93 t r e e s , A 1964 32 14 46 2 .29 (b) Traps on 251 t r e e s , A-B ' 1965 130 57 187 2 . 2 8 (c) Traps on 251 t r e e s , A-B 1966 64 50 114 1.28 (6) C o l l e c t e d as pupae on 1.16 cut and non-cut stumps: 1964 115 99 214 - 131 -for 1964 and 1965, but a s i g n i f i c a n t change occurred i n 1966. Observations made during collections may suggest an explanation for the discrepancies i n the sex r a t i o patterns. During the tree base-duff search on border trees males were found inactive i n the daytime and were most commonly near the surface of the duff layer within a radius of about 15 inches from the tree base. Females were generally on the tree base but lower i n the duff.' They appeared to spend considerable time on the root base and c o l l a r regions, presumably i n search of oviposition sites and for egg laying a c t i v i t y . During the hours of darkness both sexes may disperse l a t e r a l l y within the stand i n search of new hosts, or they may ascend the tree trunk to feed i n the crown. The greater numbers of females collected by hand searching and i n traps within the stand may -suggest that both feeding and l a t e r a l dispersion are more frequent for females than males. This may also explain why more males were found on border trees since many could have originated from the adjacent cut-over area and remained for longer periods on border trees. Tree removal on the cutover areas referred to, took place during 1961 -62 . Relative abundance of adults captured during the three and four periods of the summer are summarized i n Figures 49, 50, 51 and 52 for plots A, B, C and D. The trend for both sexes i s similar i n the two stand age classes, except that fewer males than females were generally captured during most periods of the summer. Although the general trend from spring to f a l l i s a decrease i n catch per day, the patterns vary within the same plots between years. However, the periods of catch were short and low numbers of adults were chara c t e r i s t i c of most catches. The highest catches were recorded i n June, except i n plots A and B, 1966. Although mortality may account- for F i g . 49 . Numbers of male and female adult weevils captured.throughout the summer of 1965 i n plots A and B. Fig . 50. Numbers of male and female adult weevils captured throughout the summer of, 1966 i n plots A and B. - 132 -5 Q C C U I C L Q LU CC h-C L < 5 .0 I 4.0 \-3.0 TRAPPING PERIOD, IN DAYS i 1 FEMALE > MALE o d 1 ' 10 20 JUNE 30 10 20 JULY 30 9 19 AUGUST 29 O d TRAPPING PERIODS IN DAYS 6.0 i - 1 >-< a ce ui C L o U I cc Z) I— < o in _i > U I U I 5 5.0 4.0J 3.0J 2 0 FEMALE 10 20 JUNE 30 10 20 JULY 30 9 19 29 AUGUST F i g . 51 . • Numbers of male and female adult weevils captured throughout the summer of 1965 i n plots C and D. Fig . 52. Numbers of male and female adult weevils captured throughout the summer of 1966 i n plots C and D. - 133 -- 13k -some of the rate of decrease t h i s aspect was not investigated. There was some evidence that a change i n the behavior pattern of females may have occurred i n different years i n plots A and B. Calculated numbers of female captures per day per trapping day indicated high numbers i n 196k, a s l i g h t decrease i n 1965 and a sharp decrease i n I966 (Table XXVIl). This decrease was of similar magnitude i n both p l o t s . The calculations for males suggested l i t t l e or no change i n the population levels between plots and i n d i f f e r e n t years. The data i n Table XXVII also show that the frequency of recaptures was similar for both sexes. Numbers of adult captures i n plots C and D during I965 and 1966 showed a decline for both sexes, and a change i n the sex r a t i o s (Table XXVIIl). The fact that weevil catches were higher i n the spring of I966 as compared to the f a l l of 1965 suggested that mortality did not account for a l l of the decline. I t was. therefore, l i k e l y that a combination of mortality and a change i n behavior pattern was responsible for the spring, to f a l l decline. 6 . 3 - 2 . Relationship of Trapped Adults and Tree Size: The frequency d i s t r i b u t i o n of tree sizes i n plots A and B combined i s given i n Figure 53. and male and female captures i n Figure 5^-- The tree size with greatest numbers of adult captures does not coincide with peak numbers of trees, suggesting a preference for larger trees. Both sexes are distributed s i m i l a r l y except that fewer males were captured than females. A straight l i n e relationship describes the d i s t r i b u t i o n pattern for each sex i n r e l a t i o n to tree size (Fig. 55 ) . Further evidence for selection of large trees i s i l l u s t r a t e d i n Figure 56. 6 . 3 - 3 . Dispersal Patterns of Adults i n the Forest: The analysis of adult t e r r e s t r i a l movement patterns i n plots A and B suggested that males and - 135 -TABLE XXVII. SUMMARY OF THE RELATIVE ABUNDANCE AND RECAPTURE CHARACTERISTICS OF MALE AND FEMALE H. WARRENI IN PLOTS A AND B DURING 1964-66. Plot A Plot B 1964 1965 I966 1965 1966 % females captured 1+ times 37.5 37.0 51.5 36. 8 43.2 % males captured 1+ times 59-1 33.3 44.0 4o. 0 > ^4.0 No. female captures per trap per trapping day 0.025 0.022 o.oi4 0. 027 0.016 No. male captures per trap per trapping day 0.012 0.010 0.011 0. 011 0.011 TABLE XXVIII. SURVIVAL OF MALE AND FEMALE ADULT 1964 IN PLOT ARENAS C AND D. ' H. WARRENI RELEASED IN Year Plot C Plot D Plots C + D ? 0* ? 6* ? 0* Total adults released 1964 30 20 30. 20 60 4o Sex r a t i o 1964 1.50 : 1 1.50 : 1 1.50 : 1 Total individuals recaptured 1965 24 20 22 15 46 35 Sex r a t i o 1965 1.20 : 1 1.47 : 1 1.31 : 1 Total individuals recaptured 1966 24 18 16 13 4o 31 Sex r a t i o 1966 1.33 :• 1 1.23 : 1 1.29 : 1 F i g . 53. Frequency d i s t r i b u t i o n of tree diameters of a l l trees i n the l / 5 -acre plots A and B located i n the 65-70-year old pine stand. Fi g . 54. Catch frequency of adult male and female H. warreni on different sized trees: i n plots A and B. The data were compiled from 1964, I965 and 1966,) captures. Fig. 55. Relationship between captured adult weevils and tree diameters i n plots A and B during 1965 and 1966. Lines were.fitted by the least squares method,. r value s i g n i f i c a n t of . 0 1 p r o b a b i l i t y l e v e l . * r value s i g n i f i c a n t at .05 p r o b a b i l i t y l e v e l . F i g . 56. Frequency of tree size with no adult weevil captures, with three or more captures and with fi v e or more captures. The data were compiled from plots A and B during I965 and 1966. - 137 -- 138 -females dispersed at the same rate i n feet per day (Fig. 5 7 ) . Slight differences i n the rate of dispersal may exist between plot areas (Fig. 58) as a resu l t of differences i n s i t e . The graphs suggest a pattern of random movement where the greatest distance t r a v e l l e d from a point source, such as a tree, takes place during any one night of t r a v e l . However, over long periods of time, after 8 -10 days, the rate remains constant. The average rate of linear t r a v e l for any single night for males and females compares favorably with the average distance between trees which was estimated as 8.2 feet, but does not compare with the average distance of nearest neighbor tree (4 . 0 f t . ) . The maximum linear distance recorded between trees traversed by the same weevil during one night was 37 feet. I t i s therefore possible for individuals to v i s i t more than one tree per night. Male and female individuals were also recaptured i n the same trap two nights i n succession on several occasions. The amount of a c t i v i t y , however, appeared to be limited p a r t l y by night temperatures. L i t t l e or no movement was observed when temperatures were below 40° F. When adults l e f t a tree i n search of another tree there was evidence that they moved randomly from the tree of o r i g i n , at least i n i t i a l l y (Figs. 59 a n d 6 0 ) . The chi-square test for a d i r e c t i o n a l preference showed that deviations of the calculated r a t i o s from the th e o r e t i c a l r a t i o s were not s i g n i f i c a n t at the 0 .05 p r o b a b i l i t y l e v e l (Table XXIX) for males and females separately. 6.3. 1 +. Weevil Reproduction: Experiment- 1: Tree diameter frequencies for plots C and D are shown i n Figure 6 l . The graph indicates that the two plots were very similar i n stand composition and structure. F i g . 57. Rate of dispersion of male and female adult weevils. The data from plots A and B during 1964, 1965 and I966 were combined. F i g . 58. . Rate of dispersion of male and female adult weevils separately i n plots A and B. Data were compiled from I964, 1965 and I966 captures. - 139 -' ' ' 1 1 — 1 — i — i — i — i — i — i — i — • • i i 5 6 7 8 9 1 0 1 1 1 2 '3 '4 15 16 17 18 19 2 0 21 22 2 3 2 4 2 5 2 6 DAYS 1 0 1 1 1 2 1 3 1 4 ' 5 16 17 18 19 20 21 22 2 3 2 4 2 5 26 DAYS F i g . 59. D i r e c t i o n a l movement of adult male and female weevils i n pl o t A. Data -were compiled from 1964, 1965 and 1966 captures. Fi g . 60. D i r e c t i o n a l movement of adult male and female weevils i n plot B. Data were compiled from I965 and I966 captures. - 141 -TABLE XXIX. CHI-SQUARE TEST OF DIRECTIONAL MOVEMENT OF MALE AND FEMALE ADULT H. WARRENI IN PLOTS A AND B ACCORDING TO A 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 RATIO. Plo t no. Sex Total observations D.f. X 2 P Significance P l o t A female 60 7 2.857 0 .90 to. 0 . 80 n. s. P l o t A male 28 7 10.667 0 . 2 0 to 0 . 1 0 n. s-. Plot B female 6o • 7 4 .000 0 . 8 0 to 0 .70 n. s. Plot B male 32 7 7.200 0 .50 to 0 .30 n. s. D.f. grees of 2 freedom; X = chi-square; P = probabili t y ; n. s. = not si g n i f i c a n t Observations of oviposition and egg hatch on a l l tree bases i n plots C and D are summarized i n Table XXX. Few eggs and larvae were found during the 1965 search i n both plots compared with the 1966 search. Since a l l males and females were v i r g i n when released i n 1964, and that experimental conditions were as close as possible to the natural weevil habitat, the data provide strong evidence that egg laying does not occur u n t i l the second summer of adulthood. About twice as many eggs were found i n plot C i n 1966 as compared to D of the same year, while percentage hatch was about the same for the two plots. Although fewer adults were trapped i n plot D i n 1966 (Table XXVIII) as compared to plot C there appears to be a sizeable difference i n numbers of eggs per female. I t i s suggested that by increasing the duff thickness, conditions for egg laying were enhanced. The bark surface area available for oviposition sites was increased with the Fig.. 6 l . Frequency distri b u t i o n s of tree diameters i n plots C and D. Fi g . 62. Relationship between numbers of weevil progeny per tree and tree. diameter i n plots C and D during 1966. Sphagnum mosses were . placed around the tree bases i n plot C. Lines were f i t t e d by the least squares method of a weighted regression and each v e r t i c a l bar indicates T one standard error of the mean. indicates significance at t h e - . 0 1 p r o b a b i l i t y l e v e l ; * indicates significance at the .05 l e v e l . . ' - 142 -- 1J+3 -TABLE XXX. SUMMARY OF TREE STAND, OVIPOSITION AND EGG HATCH CHARACTERISTICS IN PLOTS C AND D DURING I965 AND 1966. Ave. Total Ave. no. No. 1o eggs Plot Year Total diam. eggs + eggs + No. eggs i n trees (s.h.- larvae larvae/ larvae per hat ch niches ins.) tree female * C 1965 h7 • 2 . 1 4 0.09 0 0 . 1 7 - -C 1966 h7 - 129 2.7h 9 5-37 7 .0 7 2 . 5 D 1965 4 9 2 . 1 1 - 0 . 0 2 0 • 0 .05 - -D I966 h9 - 64 1 .31 • 5 4 .00 7 - 8 55-9 * Values i n th i s column were computed from data given i n Table XXVIII where 24, 2 4 , - 2 2 and 16 i n d i v i d u a l females were recorded i n plots C and D respectively. addition of mosses. In addition, the microhabitat around the root c o l l a r was made more moist. A higher percentage of eggs was deposited i n niches constructed by the female i n the bark tissue i n plot C as compared to plot D, and many of these were located on the c o l l a r within the zone covered by sphagnum. This indicated that females did u t i l i z e the increased bark surface area i n plot C and that females .were comparatively more active at egg laying than i n plot D. The number of eggs and larvae found i n plots C and D were l i n e a r l y correlated with stump diameter (Fig. 6 2 ) . Plot C showed a higher rate of oviposition per tree diameter class than did plot D. Experiment 2 : Out of a t o t a l of 37 eggs l a i d by females caged i n p l a s t i c cups, nearly a l l were deposited i n small niches chewed i n the bark - 144 -and covered over with excreta. Eggs were ra r e l y l a i d side-by-side. No egg hatch was observed throughout the f a l l of 1964, nor i n the spring of 1965. At the time of the l a s t examination i n the spring of I965, most eggs appeared p a r t i a l l y collapsed or destroyed. Experiment 3- Female weevils reared i n paper cups inverted over bark sections l a i d most of t h e i r eggs on the screen surface and a few were deposited i n niches chewed i n the bark. The maximum number of eggs recorded per female during a period of 84 days varied from 2 to 36 with a mean of 12.2 eggs based upon 24 female layers. On a per day basis the average number of eggs was O.236 per female per day. Using t h i s value and a possible maximum egg laying period of about 103 days, the t o t a l egg productivity during a season could be 24.3 eggs (= 103 x 0.236) per female. This may be an over estimate for females i n the natural habitat since the laboratory rearing conditions were maintained at s l i g h t l y higher temperatures and females had a r e a d i l y available food supply. The p e r i o d i c i t y of oviposition, as determined from t o t a l egg output per 10-day i n t e r v a l consecutively throughout the summer, indicated that a maximum peak of egg production occurred during the early part of July (Fig. 63). The rate of oviposition dropped rap i d l y after t h i s dafe but some eggs were s t i l l found up to August 23. During t h i s experiment a t o t a l of 294 eggs were collected from the 24 females but none of these hatched after storage i n p e t r i dishes. I t i s possible that the l e v e l of moisture was inadequate. Experiment 4: The percentage hatch of eggs l a i d by females reared i n v i a l s varied from 36 .8 to 68.4 and average 45.6 (Fig. 64). Under the F i g . 6 3 . Summer egg laying pattern of H. warreni reared i n paper cups inverted-'over pine bark during 196)4. F i g . 64. Percentage egg hatch and the period of embryonic development of H. warreni eggs stored i n moist v i a l s under natural temperature conditions. - 145 -MEAN DAY OF EGG-LAYING PERIODS - 146 -experimental conditions the average period of embryonic development was calculated as 42 days but varied from 29 to 54 days. The longest period of development was recorded from eggs l a i d during the early part of the experiment, while the shortest period was recorded for eggs l a i d during the f i n a l 10-day period. . Experiment 5: The data collected from adults reared i n p l a s t i c cages showed that almost a l l eggs were located i n the roo t - c o l l a r zone corresponding to the l a r v a l universe. However, the exact placement of the egg during oviposition varied considerably. In cages 1 to 20 (1966) about 75 percent were deposited i n niches, while i n cages 21 to 30 (1966) only 51 percent were i n niches (Table XXXl). These niches were small pockets chewed TABLE XXXI. SUMMARY OF H. WARRENI EGG LAYING EXPERIMENT IN PLASTIC CAGES ON PINE STUMPS. Year Cage nos. Starting date Dura-t i o n (days) Total °lo eggs eggs i n deposited niches Total larvae . 1o hatch No. eggs per female per day I965* 1-10 . July 5 59 164 ' 62 3 7 . 8 0 .278 • 85 I965* 11-16 July 27 38 42 - 0 0 0 .184 1966 1-10 June 21 50 121 73 8 ' 6 . 6 0.2H-2 I966 11-20 June 13 50 138 75 70 50.7 0 .276 I966 21-30 July 15 50 +5 51 0 0 0 .082 * Data from previous experiment; see Cerezke (1967) . out by the female, usually within the outer bark. The eggs were deposited i n - 147 -these niches, one per niche, and were covered with bark p a r t i c l e s or excreta. Some eggs were also loosely placed under bark scales or i n the moss immediately adjacent to the bark. The eggs were almost invariably placed singly i n each oviposition spot. These observations agreed generally with eggs observed under natural conditions i n the f i e l d . For example, i n plots C and D many eggs occurred loosely i n the s o i l adjacent to the root-c o l l a r . On one mature tree i n plot 10, f i v e eggs were found within an area of about two square inches on the root c o l l a r bark, and none of these were side-by-side. S t i l l other instances were observed where 6 - 8 first-second instar larvae were removed from similar sized areas of bark surface. This suggested that the larvae were from eggs 'deposited about the same time, and l i k e l y by the same female. .The;rate of egg laying varied considerably between cages 1 - 1 0 , 11-20 and 21 -30 of the 1966 data (Table XXXI). The low value obtained from cages 21 -30 may r e f l e c t an influence of lower temperature conditions. In general, the rates reported for cages 1-10 and 11-20 (1966) are similar to the rate observed i n Experiment 3 above. I t was not established, however, whether females were capable of laying the same number of eggs each year u n t i l death. Experiment 6: The results of 36 dissected females collected during 1964 and I965 are summarized i n Table XXXII. The data suggest that l i t t l e or no change i n the size of fat body or expansion of spermathecal gland and germaria were detected between the non-mated, non-laying condition and the mated, egg laying condition. Ovary size, t o t a l number of oocytes and the number of mature-sized oocytes showed maxima i n the late June collections. This pattern agrees with the peak period of egg production - .148 -TABLE XXXII. SUMMARY OF THE OBSERVATIONS OF THE FAT BODY AND REPRODUCTIVE STRUCTURES OF FEMALE H. WARRENI COLLECTED DURING- 1964: AND I965. Date No. Fat Ovary Total No. Length of fern- body cond- oocy- mat- of ger c o l l - ales cond- it-ion t-es ure marium ection it-ion eggs (mm) June 1 - 5 , 1964 5 S M 31 2 1.925 2 .475 3/5 - -June 2 3 -2 5 , 1965 5 M L 40 5 2.035 2.530 4/4 3 A o/4 June 30, 1964 5 S L 38 6 I . 9 8 0 2.420 4/4 3/4 1/4 July 2 2 -2 3 , 1965 5 S M 28 4 2.145 2.585 5/5 3/5 2/5 July 30, 1964 5 S M 25 2 1.925 2.420 5/5 1/3 2/3 Aug. 11, 1965 6 M M 26 0 I . 9 8 0 2.420 6/6 0/6 5/6 Aug. 31 , 1964 1 S S - 0 I . 9 2 5 2.530 - 0/1 0/1 Aug. 3 1 - ' Sept. 7, 1965 4 M M 26 0 1.925 - 4/4 0/4 1/4 * The fat bodies and ovaries ; were given general rating ;s of size small, M = medium and L = large. The c r i t e r i o n of ovary size was based upon counts of oocytes per four ovarioles present i n each female as follows: S = 1 2 - 2 4 ; M = 25 -36 and L ,= 36+ oocytes. The fat body and oocyte ratings represent an average for each c o l l e c t i o n group of females. Length Propor- Spermatophore of sper- t i o n present mat-hecal mated gland . F r e s h 0 M (mm) - 149 -described i n Figure 6 3 . Mated and non-mated females were c l e a r l y discernable by the presence or absence of sperm i n the spermathecal gland. In addition,- freshly mated females possessed a single spherical shaped spermatophore which expanded' the vaginal pouch and was whitish i n appearance. . These were observed most commonly during June. At least two females i n the f i r s t c o l l e c t i o n had not mated. As the summer progressed the number of freshly deposited spermatophores decreased but they were s t i l l recognizable, being smaller i n size, yellowish i n color and irregular i n shape. The most active period of mating appeared to be throughout June and part of July. Spermatozoa were found i n the spermathecal glands of a l l females except two from the e a r l i e s t c o l l e c t i o n ; these two were l i k e l y newly developed females. 6 . 3 . 5 Light and Temperature Response and Orientation of Adults: Experiment .1: The d a i l y numbers of captured adults i n plots C and D were correlated with temperatures at each hour-interval of the previous night. The data indicated that temperatures recorded at 11:00 p.m. provided the highest correlation coefficient (r) value (Fig. 6 5 ) . This suggested that most emergence from the duff occurred shortly p r i o r to t h i s hour. Figure 66 describes the relationship between weevil numbers captured and temperatures recorded at 11:00 p.m. of the nights p r i o r to collections. The graph shows that few weevils were caught when the temperature f e l l below 36-hO °F by 11:00 p.m. Experiment 2 : -When adult weevils were placed under moss i n the center of a small arena the i r maximum peak of emergence through the moss occurred between 10:00 and 10:30 p.m. (Fig. 6 8 ) . This corresponded to about Fig.. 6 5 . Correlation of adult weevils captured i n plots C and D with night temperatures. Fi g . 66. Relationship between adult weevil catch i n plots C and D and temperatures recorded at 11:00 p.m., Mountain Standard Time. Line f i t t e d by least squares method, r value s i g n i f i c a n t at 1 percent l e v e l . T E M P E R A T U R E F ° A T II R M . , M.S.T. 151 -two hours after sunset. Light in t e n s i t y recordings taken concurrently indicated a possible relationship with weevil emergence. Throughout the experiment a l l temperatures recorded were above kO °F. Several adults emerged pri o r to sunset and some of these began movement as soon as they were placed i n the arena. At least some of this i n i t i a l behavior may be abnormal i n that i t appeared to be i n response to disturbance through handling. Many weevils climbed v e r t i c a l l y through the moss while others crawled l a t e r a l l y . Once at the exterior of the moss they invariably stopped a l l movement for a few minutes to over half an hour. Some weevils, especially those that emerged from the top, assumed a characteristic pose as i f seeking out some aspect of the habitat. They extended the i r antennae, stood motionless for a few minutes and then began a turning movement. Following t h i s the weevil either relaxed i t s antennae and remained motionless for a short period, or commenced crawling horizontally. Once l a t e r a l crawling had begun most weevils continued i n a straight l i n e with l i t t l e deviation from t h i s d i r e c t i o n a l path u n t i l an obstruction was' met. . The d i r e c t i o n a l response, of adults i n the arena i s analysed i n Figure 67. There i s evidence that the weevils chose the dire c t i o n of the pine tree more .consistently than any other direction. Experiment 3 : Some general patterns of behavior were summarized from the adults retained i n a small arena enclosing two pine trees. Nearly a l l observable a c t i v i t y of the adults occurred between the hours from 7 :00 p.m. to 5:00 a.m. during the three day experimental period. Greater attractiveness to the larger tree than to the smaller tree was common to both sexes. Females appeared to be more active than males i n t e r r e s t r i a l movement; i. e . , 58 percent compared to k6 percent for males. Males were more abundant F i g . 67 . D i r e c t i o n a l response of adult H. warreni confined within a 90-cm. diameter arena. Fi g . 68 . Numbers of adult H. warreni emerging from moss i n r e l a t i o n to time during the evening. Decreasing l i g h t i n t e n s i t y before and after sunset i s also described. - 152 -TO POST • 280 80 DISAPPEARANCE OF SUN x \ -2 - 153 -on the large tree than females; i.e., 50 percent compared to 30 percent o f female s. The time of i n i t i a l evening a c t i v i t y varied widely but the peak period occurred between 10:00 p.m. and 1:00 a.m. Several weevils were observed at the 2 1 . 5-foot l e v e l above ground on both trees. The speed of crawling upon the host was slow. For example, one male ascended a distance of f i v e feet on the tree stem i n 12 minutes. During t h i s period 5 - 6 stops were made, each 3 - 5 seconds i n duration. Feeding was observed on branches of the smaller tree a few inches from the main stem. Adults i n the mating position were observed up the tree, on the ground surface and i n the duff. 6 . 3 . 6 . Adult Feeding Patterns: Experiment 1: The feeding patterns of adults on two co-dominant trees, 20-25-years old, are analysed i n Figures 69 and 7 0 . The arena around tree A was established e a r l i e r than for tree B, thus accounting for the lower values on B. Both trees show a similar pattern with two peaks of almost equal height. This suggested that adults fed mostly on the lower and on the upper branches. Many of the l a t t e r feeding sites occurred i n the terminal buds where females were more commonly observed than males. The distance out on the branch from the main stem was also variable but some pattern i s evident (Fig. 6 9 ) . In general the feeding scars were farthest out on the lower branch whorls. Natural needle drop extended farthe out on the lower branches and th i s may have influenced the distance for feeding since the needles impeded th e i r movement on the bark surface. Few scars were found among needle covered areas. During movement or when at F i g . 69. Pattern of adult weevil feeding scars on branches i n r e l a t i o n to height above ground. Fi g . 70. Frequency d i s t r i b u t i o n of adult weevil branch feeding scars i n r e l a t i o n to height above ground. 1 - . 1 5 5 •-r e s t on a branch the adults clung tenaciously, indicating a preference for a s o l i d substratum. Nearly a l l feeding scars were located on the upper surface of branches. Experiment 2: Although adult feeding i s i n s i g n i f i c a n t i n i t s effect on trees some terminal shoots may become distorted as a resul t of feeding (Fig. 7 1 ) . In addition to branch and terminal bud feeding, adult scars have also been observed on the root base and c o l l a r regions. When adults were retained i n two-foot-square arenas only two pine seedlings showed evidence of feeding. This damage was considered n e g l i g i b l e . This indicated that l i t t l e or no damage would occur to pine seedlings i n newly cutover areas from adults emerging from cut stumps, or from adults immigrating from adjacent areas. 6 . 3 . 7 . M o r t a l i t y Factors of Adults: L i t t l e i s known of the mortality factors of H. warreni adults, and the trapping studies i n plots C and D indicated a l i f e span of at least three years. The p o s s i b i l i t y of Beauveria bassiana has been mentioned (see section 6.1.4.) and i s i l l u s t r a t e d i n Figure 72 . The examination of stomach contents of shrews (Sorex cinereus cinereus) provided no evidence of adult weevil predation. S c l e r i t a l fragments of carabid beetles were a common constituent of the gut contents and these were e a s i l y i d e n t i f i e d . One female weevil collected for dissection had 10 i n t e r n a l parasites (Fig. 73) within i t s abdominal cavity and external to the digestive t r a c t . The parasites were subsequently i d e n t i f i e d as nematodes belonging to the family Tylenchoidea by Dr. Gertrud R. Kloss, Sao Paulo, B r a z i l , and v e r i f i e d by Dr. W. Ruhm, Hannover, Germany (personal communications). According to F i g . 72 . Dead adult H. warreni showing the white mycelial mass of the fungal parasite, Eeauveria bassiana. (X 5 ) . F i g . 73- Nematode parasite (family Tylenchoidea) found within-the abdomen of a female adult weevil. (X ho). - 156 -F i g . 71- Adult weevil feeding damage on terminal shoots of 6-8-year old lodgepole pine. - 157 -- 158 -Dr. Kloss the nematode parasite stage i n the weevil i s hermaphroditic while the succeeding stage would "be gonochoristic and would be spertt i n the s o i l . The effect of the parasite upon the health of the weevil i s unknown but i t i s almost certain to affect fecundity since each nematode measured about three mm. i n length. Most, of them occupied the region of ovary expansion i n the dorsal abdomen. Externally attached mites were common on the-adult weevil and appeared most abundant after June. Out of 7^ mites collected 72 were on females and only two were on males. A sample of 12 specimens was i d e n t i f i e d by Dr. E. E. Lindquist, (personal communication) Ottawa, Canada, as Saproglyphidae, Carpoglyphinae : H e r i c i a sp. (near H. fermentationis V i t z . ) . Dr. Lindquist indicated that the externally attached mite's were an immature form and that the adult form may l i v e upon the sap oozing from the trees. The effect of the mite upon the weevil may be negligible and i t s presence may be primarily for dispersion. 7. Studies of the Effects of Weevil Damage to Trees 7 . 1 . Anatomical E f f e c t s : Several inherent mechanisms of lodgepole pine appeared to be evident, i n helping to overcome the damaging effects of the weevil. One effect i s i l l u s t r a t e d i n a cross-sectional view of a cut stump from the 65-70-year old stand (Fig. 7k). Periods of attack on t h i s stem were dated since the age of 28 years, and heaviest damage occurred at the age of ^ 3 - ^ 5 years. At t h i s time 50 percent or more of the root c o l l a r was girdled to xylem tissue. P a r t i a l recovery from the loss of the perimetrical distance of cambial and phloem tissue since age 4-3-"+5 was brought about by a - 159 -Fig. jh. Cross-sectional view of a 66-year old pine stump cut at the root c o l l a r l e v e l . Numbers beside the l a r v a l feeding scars indicate approximate years of attack. Note bud-like growth pattern of wood increment adjacent to scar areas. - i6o -budding type of growth adjacent to the wound areas. Rate of growth of both r i n g width and l a t e r a l extension of cambium i n the "bud" areas was greatly increased over the normal growth pattern. This had the effect of p a r t l y .sealing o f f damaged areas, and at the same time, helped to increase l a t e r a l l y the area of conductive tissue. A second mechanism of defense occurred i n response to wounding, r e s u l t i n g i n the formation of traumatic r e s i n ducts (Figs. 75 and 76). Large numbers of v e r t i c a l ducts were produced i n the outermost xylem ri n g when l a r v a l feeding extended through the cambial tissue; t h e i r production.may occur annually u n t i l l a r v a l feeding i s terminated. Traumatic ducts were found to extend above and below the wound area and were a source of the re s i n which exuded at wound openings. As a resu l t open wound 'areas appeared r e l a t i v e l y resistant-to entry of fungal decay organisms. In addition to surface resinosis, some i n f i l t r a t i o n of the tracheitis with r e s i n occurred co n t r i p e t a l l y from the wound (Figs. 77 and 78).. This was observed especially i n young stems when damage extended through the cambial layer. Such areas were often pie-shaped i n the transverse plane and extended toward the p i t h . Resin-soaked xylem areas were observed to extend above and below the wound area. A t h i r d mechanism of defense was observed on wound damaged trees i n the Strachan area west of Rocky Mountain House, on a 15-year old pine (Fig. 79) and on several mature pine (Fig. 80). These trees developed adventitious- roots d i r e c t l y above the wound areas. They may function to p a r t i a l l y compensate for the loss of w e e v i l - k i l l e d roots and damaged co l l a r regions. Many trees sampled i n plots 1 to 5 which had severe damage around F i g . 75 - Wood discs cut at two-inch- intervals up the main stems of 2 0 -year old pine trees, i n the Robb Burn. Upper three ( l e f t to right) were removed from a weevil damaged tree; the lower three from a non-attacked tree. Note the large, number of v e r t i c a l traumatic r e s i n ducts produced i n the two outer growth rings of the attacked tree. Resin ducts were made more c l e a r l y v i s i b l e with a starch-reacting stain of iodine (O.k gms. I 2 + 1 .8 gms. K l per 100 ml. water). Ruler scale i s i n inches. . ', Fig . 76 . Transverse section of a disc cut' at root c o l l a r l e v e l from a weevil attacked tree showing a' portion of the outer four wood increments. Note the v e r t i c a l traumatic r e s i n ducts (accentuated by the starch-staining iodine solution) i n the outer two increments. The formation of two tangential bands of traumatic ducts are evident i n the f i r s t and second rings. (X 1 2 ) . F i g . 77 . Radial view of the lower stem of a weevil attacked. 20-year old pine tree. Note wound area on the:-foot c o l l a r and resin-soaked sapwood. Fig. 78 . Transverse view of discs removed from the taproots of a weevil damaged tree ( l e f t ) and a non-attacked tree ( r i g h t ) . Note the l i g h t colored resin-soaked sapwood areas on the attacked tree. Scale i n inches (upper) and mm. (lower). - 162 -Fig. 79. Lower portion of a stem from a 15-year old pine tree showing small adventitious root development immediately above a weevil l a r v a l wound. Fig . 80. Lower portion of a stem from a 95-100-year old pine tree showing a small adventitious root immediately above a weevil l a r v a l wound area on the root c o l l a r . The large l a t e r a l root v i s i b l e on the l e f t was k i l l e d from l a r v a l feeding. - 163 -- 164 -the root c o l l a r showed a s l i g h t swelling above the wound or a reduction i n growth within the wound region. For example, one 12-inch diameter tree had a root c o l l a r circumference of 41 inches around the damaged l e v e l while immediately above the wounds, the circumference was 42 inches. 7 . 2 . Growth Loss Effects: The assessments of weevil l a r v a l feeding damage to pine was made with respect to p a r t i a l l y girdled stems at the root c o l l a r zone. A l l pine trees were i n the dominant and co-dominant categories. Table XXXIII shows the pooled measurements of attacked and non-attacked groups of trees. The data indicate a f a i r l y homogeneous selection of trees. The percentages of root co l l a r s girdled were 4 5 - 7 for the Robb Burn trees and 4 9 . 0 for the Grande P r a i r i e trees. Average years of i n i t i a l damage were 1961 and 1963 for the two areas respectively. Data presented i n Table XXXIV suggests that attacked trees on the average (except 1965 branches) produced more l a t e r a l branches on the top whorl than did non-attacked trees. However, the differences are small, especially on the Grande P r a i r i e sample. I t was noted that i n t h i s sample, internodal branches were more common than i n the Robb Burn sample and this may have .influenced the growth pattern. There were no appreciable differences i n lengths of needles on the I963 and 1964 l a t e r a l branches of the top and second top whorls between attacked and non-attacked trees from the Robb Burn (Table XXXV). Terminal and l a t e r a l branch length measurements indicated a reduction i n the attacked tree groups as compared with the controls. In general, shoot elongations showed an annual decrease on both terminals and l a t e r a l s for the two and three year periods of the Robb Burn and Grande P r a i r i e areas respectively. - 165 -TABLE XXXIII. MEASUREMENTS OF WEEVIL ATTACKED AND NON-ATTACKED TREES IN THE ROBB BURN AND GRANDE PRAIRIE STUDY AREAS. Ave. Ave. diam. % root Ave. year Area Tree group Ave. age height at s.h. co l l a r f i r s t (years) ( f t . ) (ins.) girdled attack Robb Attacked 20.4 15.8 2.33 5^-7 1961 Burn (trees1A-10A) (20-21) (12.6-18.7) (2.07-2.54) (27-62) (1957-196U) Non-attacked . 20.6 16.4 2.25 _ _ (trees LN-10N) (17-23) (13.2-19.4) (1.85-2.39) - -Grande Attacked 21.7 20.7 2.39 49.0 1963 P r a i r i e (trees 1A-11A) (19-24) (17.2-25.8) (2.40-3A0) (28-64) • (.I96I-I965) Non-attacked 22.0 20.8 2.85 _ _ (trees 1N-10N) (19-24) (17.3-24.8) (2.50-3.20) - -Values i n brackets indicate range of measurements. TABLE XXXIV. NUMBERS OF LATERAL BRANCHES ON THE TOP WHORL OF ATTACKED AND NON-ATTACKED TREES IN THE ROBB BURN AND GRANDE PRAIRIE AREAS. Tree Ave. number of l a t e r a l branches on the top whorl Area group 1963 1964 1965 1966 Robb Burn Grande P r a i r i e Attacked Non-attacked Attacked Non-attacked h.5 3-9 h.7 4.2 4.6 4.4 3.8 h.3 4.4 4.2 - 166 -TABLE XXXV. NEEDLE LENGTH, TERMINAL LEADER AND TOP LATERAL BRANCH LENGTHS OF ATTACKED AND NON-ATTACKED TREES IN THE ROBB BURN AND GRANDE PRAIRIE AREAS. Area and Ave. needle Ave. terminal length Ave. l a t e r a l branch tree group length (mm) (i n s . ) . length (ins.) 1963 1964 I963 1964 1965 1966 I963 1964 1965 I966 Robb Burn Attacked . 6 5 . 1 6 9 . 8 15.5 l 8 . 2 - - 7 .2 8 . 5 ( 8 . 9 ) ( 1 2 . 9 ) (12.2) (14 .1) Non-attacked 67 .0 7 0 . 0 .17.2 2 0 . 9 - - 8 .2 9 . 9 Grande P r a i r i e Attacked - - - 15.1 13 .3 14 .1 (10.1) (3 .6 ) (17 .5) Non-attacked - - - 1 6 . 8 1 3 . 8 ' 17.I Values i n brackets indicate percentage reduction based upon non-attacked tree lengths. • ' • Attacked trees i n the Robb Burn showed a decrease i n terminal lengths of 8 . 9 -1 2 . 9 percent, while l a t e r a l elongations were decreased by 12 .2 - 14 .1 percent. Reduced elongations of terminals of attacked trees from the Grande P r a i r i e area ranged from 3 - 6 to 1 7 - 5 percent, while l a t e r a l s were reduced from 1 .3 to 3 .0 percent. Over the two and three year periods of measurements recorded from the Robb Burn and Grande P r a i r i e areas respectively the mean losses of tree heights were estimated as follows: Robb Burn: 2 .2 ins. per year or a t o t a l of 11 .5 percent-Grande P r a i r i e : 1 .7 ins. per year or a t o t a l of 10.9 percent 7 - 4 6 . 5 7 . 5 ( 1 . 3 ) ( 3 - 0 ) ( 2 . 6 ) 7 - 5 6 - 7 7 - 7 - 167 -The patterns of growth increment for the oblique sequence are shown in Figures 8 l , (a) to (e) and 82, (a) to (g) for the Robb Burn and Grande P r a i r i e areas. Both graph series indicate a pattern of decreasing widths • from the e a r l i e s t increment to the l a s t of attacked tree groups as compared with controls. The quantitative changes of mean annual widths of each increment are given i n Table XXXVI. TABLE XXXVI. . AVERAGE RING THICKNESS PER YEAR AND PER TREE GROUP OF ATTACKED AND NON-ATTACKED TREES AS DETERMINED FROM OBLIQUE SEQUENCE MEASUREMENTS. Area and Ave. yearly oblique sequence ri n g measurements (mm) tree group I958 1959 i960 I96I 1962 I963 1964 1965 1966 Robb Burn Attacked 2 .15 2 .02 - - 2 .65 2 . 2 8 2 .49 Non-attacked 2 .22 2 .19 - - 2 . 8 l 2 .47 2 . 9 9 NA - A * +.07 +.17 +.16 +.19 +.50 Grande P r a i r i e Attacked - - 2 .37 2 .42 2 .37 2 .39 2 . 2 9 2 .27 1-90 Non-attacked - - 2 .12 2 . l 8 2 .22 2 .27 2.24 2 .34 2 .12 NA - A * - . 2 5 -.24 - . 1 5 - . 1 2 - . 0 5 +.07 +.22 * NA - A = non-attacked minus attacked values, I t was noted that trees from the Robb Burn did not show the f u l l c haracteristics of the oblique sequence pattern as described by Duff and Nolan (1953 )3 while the Grande P r a i r i e sample trees did (Figs. 8 l and 8 2 ) . F i g . 8 l . (a) to (e). Oblique growth sequence patterns of attacked and non-attacked trees from the Robb Burn. Graphs (a) and (b) represent pre-attack years; graphs (c), (d) and (e) represent post-attack years. The mean year of attack occurred i n 1961. - 168 -i 5 I 1 i i i i i i 7 8 9 10 II 12 13 S T 4 . 0 r I 2 3 4 5 6 7 8 9 10 II 12 13 S T l . s I I I I I I I I I I I I I I I I 2 3 4 5 6 7 8 9 10 II 12 13 S T 4.5r INTERNODE FROM T R E E TOP F i g . 82 . (a) to (g). Oblique growth sequence patterns of attacked and non-attacked trees from the Grande P r a i r i e area. The mean year of attack occurred i n 1963. - 170 -The.horizontal growth sequences shown i n Figures 83 and 84 do not indicate a clear description of the attack periods. Only a s l i g h t indication of a gradual widening of the two lines i s evident i n Figure 83, p a r t i c u l a r l y since 1961 for the Robb Burn trees. Figure 84 shows a similar s l i g h t divergence of lines after 1963. • • • Figures 85 and 86 depict the v e r t i c a l sequence patterns and provide the best indication of the three growth sequences i n expressing the effects of weevil damage on pine. In the Robb Burn sample a sharp deviation from the control group i s indicated after the 1961 increment. In contrast, the greatest deviation from the control group of the' Grande P r a i r i e sample occurs between 1961 and 1963. These patterns agree reasonably w e l l with the average years of i n i t i a l attack shown i n Table XXXIII. The data suggest that growth loss effects on trees having approximately 50 percent of the root c o l l a r circumference girdled may appear i n the f i r s t or second year after damage. Figs. 83 and 8k. Radial growth sequence patterns at the lO^inch stump height l e v e l of attacked and non-attacked trees. F ig. 83 (top) describes the pattern of trees from, the Robb Burn; Fig. 8k (bottom)'describes the pattern for the Grande P r a i r i e trees. - 171 -Figs. 85 and 86. V e r t i c a l growth sequence patterns of attacked and non-attacked trees. The second increment from the p i t h at each internode was used for a l l measurements. Fig. 85 (top) describes the pattern i n trees from the Robb Burn where the average year of attack was 1961. Fig. 86 describes the pattern i n trees from the Grande P r a i r i e area where the average year of attack occurred i n 1963. - 172 -1965 1963 1961 1959 I I 4 I I 1 * j i i i i i i i i i i i i i I 2 3 4 5 6 7 8 9 10 II 12 13 ST. INTERNODE FROM TREE TOP 1966 1964 . 1962 , I960 • i ' ' I I I 1 1 1 1 I 2 3 4 5 6 7 8 9 10 ST. INTERNODE FROM TREE TOP - 173 -DISCUSSION The geographical d i s t r i b u t i o n pattern of H. warreni i n Alberta agrees generally with e a r l i e r studies (Ann. Rpt. Forest Insect and Disease Survey 1956; Stark' 1959b). Although the d i s t r i b u t i o n of lodgepole pine extends to w e l l over 6000 feet i n elevation i n the Alberta f o o t h i l l s (Rowe 1959) i f was not determined why the weevil was generally absent above 4500 feet. Descriptions of these higher elevations provide some clues. The Upper F o o t h i l l s Section (B .19c of Rowe 1959) forms a sharp t r a n s i t i o n a l zone between the Lower F o o t h i l l s Section and the Subalpine Region (Horton 1956) . This section t y p i c a l l y has high forested h i l l s up to 6000 feet with deep valleys between 4000 and 6000 feet. Major vegetation differences as compared to the Lower F o o t h i l l s include a greater proportion of white and black spruce and a lower incidence o f poplar species. Thus the rapid t r a n s i t i o n a l change toward a dominant, spruce species complex of the Subalpine Region l i k e l y contributes to an unfavorable- environment for weevil survival. There i s evidence from the present studies that white spruce i s attacked secondarily to pine i n the Alberta f o o t h i l l s , and that black spruce i s attacked only occasionally. Temperature data (Smithers 1962) suggest that- mean summer s o i l temperatures decrease with increasing a l t i t u d e and with increasing stand density ( M i l l e r s 1965). This would have the effect of increasing developmental time of immature stages. Studies i n Nordic countries have demonstrated that- the length of the developmental time and the l i f e cycle of H. abietis i s largely dependent upon temperature (Nordic Forest Entomologists' Research Group I962). I t i s also possible that the t o t a l summer period of - 174 -favorable night temperatures for adult a c t i v i t y ( i . e . , temperatures above 36 - kO °F) relates inversely to a l t i t u d e . Other l i m i t i n g factors may be related to the ground vegetational and physiographic differences described for the higher elevations (Horton 1956; Smithers 1962) . Within the Lower F o o t h i l l s Section natural stocking of lodgepole pine varies widely but stand density i s generally lower and crown d i f f e r e n t i a t i o n i s better than i n the Subalpine (Smithers 1962). The reasons for these differences are unknown but i t was suggested that they are due to s o i l , species composition, especially the abundance of poplar, and possibly to genetic differences. Heavy overstocking occurs .on mesic and dry sites (Horton 1956), but these sit e s on the whole, have not been as favorable to the weevil as moist s i t e s . The fact that no H. p i n i c o l a adults were found on lodgepole pine strengthens the view that t h i s species inhabits moist sites characterized by spruce and-larch species. I t i s therefore u n l i k e l y that immature stages of t h i s insect occurred i n the population samples of H. warreni. The detailed analysis of the weevil habitat i n the 65-70-year old and i n the 20-25-year old stands provided a basis from which to judge habitat-relationships with weevil abundance elsewhere. However, even within these two stands weevil habitat conditions were highly varied and complex. Apart from the dominant pine host tree growing i n an even-aged condition, certain other characteristics common to both areas may be singled out as favorable weevil s i t e factors. In general, the highest weevil incidence occurred where the ground f l o r a l complex was r i c h and where s o i l conditions were moist. These site s usually had a strong component of moss species mixed with a variety of herb species. This supports the studies of Warren (1956b) i n - 175 -white spruce habitats. Pine areas with a forest f l o o r carpet of predominantly moss species did not appear as favorable a s i t e as did a more varied f l o r a l carpet. This may have been due to excess moisture. Uneveness of a forest floor may constitute an important characteristic of a weevil habitat, especially i f decaying logs are abundant. Warren (1956b) pointed out the importance of these logs lying adjacent to successful l a r v a l feeding s i t e s , and the studies i n plots 1 to 5 p a r t i c u l a r l y bore t h i s out. The data suggested that the logs provided extra moisture to the l a r v a l universe and also added protection.to pupae• against excess moisture and parasites. Warren suggested that the .adult weevil sought out the moister sites for placement of eggs. I t was postulated that the.weevil habitat changes i n time with, and i s p a r t l y dependent upon the age of the stand when destroyed by f i r e . F a l l e n burnt snags 80-years old, for example, would l i k e l y create a more favorable habitat i n the new stand than would f a l l e n burnt snags 40-years old. The larger snags provide.deeper and larger depressions when they f a l l and decay more slowly. Thus the former sit u a t i o n may be longer l a s t i n g i n i t s effects upon the habitat.• I t i s reasonable to suppose that, i n intensely managed pine forests of the future, the f a v o r a b i l i t y of weevil habitats may be reduced since there would be l i t t l e or no uprooting as i n many of the present day stands preceded by f i r e . Several sources of error were inherent i n the sampling system. The tree as a basic sampling unit varied i n size, i n r o o t - c o l l a r surface area, i n root branching patterns and i n depth of root submergence below the forest f l o o r . These aspects give r i s e to an ever changing mieroenvironment - 176 -i n the ro o t - c o l l a r zone of each tree. In a l l p r o b a b i l i t y they accounted for much of the v a r i a b i l i t y i n weevil numbers within plots, as w e l l as between plots. Another source of error was related to the ease'with which different l i f e stages were located. Large larvae and pupae were generally easy to locate, while early instars required extra fine scrutiny of the roo t - c o l l a r surface. In addition, some trees showed evidence of heavier previous attacks than others. This was especially true of larger trees where thick accumulations of hardened resin-soaked s o i l often ringed the c o l l a r zone for 3-k inches. These masses required considerable e f f o r t to chip them loose, thus giving r i s e to di f f e r e n t t a c t i c s i n sampling procedure. The greatest sources of error appeared to have involved the early instars as suggested by the frequency d i s t r i b u t i o n of head capsule widths. Since sample trees were selected randomly i t was not l i k e l y that systematic errors arose as a re s u l t of 'improper representation of tree sizes, even though weevil numbers were biased toward larger trees. I t appeared that the sample trees followed the same size gradient as i n the natural habitat. There seems l i t t l e doubt that weevil populations were maintained at c h a r a c t e r i s t i c a l l y low numbers. I t i s doubtful that the r e l a t i v e l y small r o o t - c o l l a r universe could account for t h i s alone since a large portion of the p o t e n t i a l feeding sites were not u t i l i z e d i n any one year. There was also no evidence i n plots 1 to 7 of a vio l e n t s h i f t i n weevil numbers between years. Only s t r i p C of plots 1 to 5 i n the 1965 sample showed a marked change i n weevil abundance, and i t was suggested that this occurred i n response to an a r t i f i c i a l s ituation created by clearcuttlng. Weevil abundance recorded i n 85-90-year old pine stands i n 1957 - . 177 -within the v i c i n i t y of plot 10 was comparable to those i n plots 1 to 5 during 1 9 6 l to 1965. In undisturbed stands the average number of larvae per tree varied from 1.25 to 2 .86 (x = I . 8 3 ) (Stark 1959a) while the estimates per acre were mostly within the range 600 to 1200 weevils. In a variety of other mature stands sampled along the Alberta f o o t h i l l s by Stark (1959a) similar population levels were recorded; numbers of larvae per tree varied from 1.00 to 2.kk. In plantations of Scotch, jack and red pines i n the eastern United States populations of Hylobius r a d i c i s have generally been higher. In Scotch pine they varied from 6 to 8 weevils per tree (Maxwell and MacLeod 1937; Schaffner and Mclntyre 1944) . Other-values reported have been i n terms of numbers of larvae per inch circumference ( M i l l e r s 1965) . These values varied from 0 . 2 3 to O.96 larvae. I t i s worth noting that p l o t 10, sampled i n I966, was' located within the Block number 5 area sampled by Stark i n 1957- His data ( l 9 5 9 a ) showed that the population l e v e l was 1 . 9 1 larvae per tree or 1226 larvae per acre. The 1966 data suggested that weevil abundance was less than one-quarter that observed i n 1957- While i t i s impossible to-ascribe a reason for t h i s decline, certain s i g n i f i c a n t changes were noted i n the stand i n 1966.. . Tree density per acre had been reduced from 642 to 6 l 0 stems per acre since 1952 (Crossley 1955), while the mean diameter increase (d.b.h.) during this 14-year period was estimated at only 0 . 3 inches. The stand appeared i n a general state of decadence as the crowns were, very thi n and dead snags were evident i n most diameter classes. In addition, many sampled trees had one or more major l a t e r a l roots k i l l e d by the g i r d l i n g a c t i v i t y . of weevil larvae. - 178 -The attack density patterns and tree size relationships were evident i n two dimensions; according to stand age and according to habitat-s u i t a b i l i t y . . Within each stand type weevil numbers increased with tree size, regardless of stand age. In young stands the largest trees supported the most weevils as did the.largest trees i n the older stands, but fewer weevils per tree were char a c t e r i s t i c of the younger stands. Stands of the same age ( i . e . , plots 1-5, 6 and 7) d i f f e r e d from one another by s u i t a b i l i t y of habitat; the less suitable ones carried fewer weevils per:-tree. The absolute estimates of weevil numbers per acre indicated that, although weevil numbers increased with tree size, similar levels of abundance were found i n young and old stands. This suggests that weevil abundance remains r e l a t i v e l y constant i n time. Stand density changes i n time as a . r e s u l t of natural thinning processes, and as each surviving tree grows, i t s capacity to support more weevils increases. I t i s therefore l o g i c a l to assume that the rate of increase i n weevil numbers per tree i s i n proportion to tree mortality and i n proportion to the rate of increase of habitat space due to tree growth. The reason for a peak development of weevil abundance 'at 426-506 stems per acre i n the 65-70-year old stand i s d i f f i c u l t to explain since it-i s l i k e l y inherent i n several variables which evolve with successional changes during stand development. I t might be postulated that- "optimum conditions" of 426-506 trees per acre represent a balance between minimal tree spacing and maximum stem diameter; the former characteristic may relate to adult weevil-host and mate finding e f f i c i e n c y while the l a t t e r factor may relate to t o t a l habitat space available for egg laying and l a r v a l feeding - 179 -s i t e s . M i l l e r s (1965) noted also thatl.there were stand density effects which influenced the abundance of H. r a d i c i s . He suggested that cooler s o i l temperatures associated with dense stands as compared to open grown stands may be the reason for a near absence of t h i s weevil i n dense stands. I f lower s o i l temperatures i n dense stands reduce the rate of l a r v a l and pupal development, greater mortality could be expected i n the pupal stage. Evidence for t h i s was given i n Figure kO and from the fact that no pupae were ever found to overwinter successfully. Stand density relationships i n young pine were not s u f f i c i e n t l y clear to compare with that of mature pine. However, i t i s possible that the r e l a t i v e importance of tree density i n maintaining populations i n young stands may not be of the same magnitude as i n older stands. The duff depth factor appears to play a key role i n defining the l i m i t s of the feeding and developmental zone of immature weevil stages upon the host tree. I t i s no less important to the adult since most of i t s inactive period as w e l l as some active periods are spent i n the duff. In general, i t i s the duff layer which adds protection to a l l stages of the l i f e cycle. The duff layer may vary i n both quantity and i n quality, depending upon the f l o r a l complex, s o i l conditions, stand density and stand maturity. Thus the relationship of weevil numbers and duff depth i s interrelated with these other factors. T h e 3 d i s t r i b u t i o n of duff depths around the bases of different sized trees within the same stand suggests an explanation for the changing slope of l i n e observed i n Figure 22 . The greater proportion of 12-inch diameter trees with thick duff provides a proportionately larger r o o t - c o l l a r surface area, and hence, a proportionately larger l a r v a l universe i n - l8o -comparison with smaller diameter trees. This explanation may apply equally w e l l to the pattern of weevil d i s t r i b u t i o n on both c o l l a r and root regions. There was evidence that the proportion of weevils on roots and c o l l a r regions varied from year to year and between stands. The differences observed i n plots 1 to 10 may be p a r t i a l l y explained by the fact that some years were more moist than others. I t might be postulated that during dry years, or during dry intervals of the summer, oviposition may occur farther down the roots, or lower on the c o l l a r . S i m i l a r l y , larvae may respond i n a comparable manner to avoid or seek out more moist conditions. Thus the time of sampling during a season or i n d i f f e r e n t years may account for some of the observed v a r i a b i l i t y . In contrast to these studies Stark (T959 a ) observed 85 percent of larvae on roots and only 13 percent on the root ' c o l l a r . His data, however, included trees of a l l sizes. Warren (personal v communication) noted that the roots of white spruce were more severely damaged than the roots of jack pine, where as the root c o l l a r of jack pine was preferred more by the weevil than the root c o l l a r of white spruce. Data analysed from plots 1 to 5.suggested that the proportion of weevils on the roots tended to increase with tree size. This may result from two things. F i r s t l y , i t may relate to the duff depth d i s t r i b u t i o n as mentioned e a r l i e r . Secondly, i t may be due to the larger root sizes upon which there i s greater expansion of egg laying a c t i v i t y . In the clearcut s t r i p s of plots 1 to' 5 i t was u n l i k e l y that any successful oviposition occurred on the cut stumps during I962 and 19^ 3, so that most of the weevils collected i n 1963 were from eggs l a i d during the . summer of 1961. This indicates that at least two years are necessary for - 181 -to adult egg development. Other workers have postulated a similar developmental period (Reid 1952; Warren 1956b and Stark 1959b). The question may be asked what happens to adult weevils after tree removal. There was evidence that some adults migrated from the cut area to adjacent non-cut trees. Evidence for this migration was provided i n the population sample i n s t r i p C of plots 1 to 5 between 1963 and 1965, and from collections of adults on border trees. A similar pattern of events l i k e l y occurred i n plot 8 after the clearcut operation of 1957-58 . The population l e v e l recorded i n t h i s plot was higher than reported elsewhere. Further evidence of adult migration was given by Stark (1959b) who suggested that the effect of a cutting method which reduced the number of stems per acre resulted i n concentrating the population i n the r e s i d u a l trees. In plots 1 to 5, I965 i t appeared u n l i k e l y that the increase i n the C s t r i p s was due to migration of adults from within the stand. Populations i n the D s t r i p s showed a f a i r l y uniform trend of increase from I961 to 1965, and any movement into C was probably normal. The changes i n weevil abundance within stands of di f f e r e n t degrees of maturity appear to be effected through two main variables of stand development; stand density.and tree growth. The rate at which natural thinning takes place appears to be extremely variable (Smithers 1962) and no reports were found which suggested a consistent pattern. The analysis of old weevil scars by dating on 65-70-year old trees suggested that populations increased most rapidly between the ages of 30 and 1+5 years, while r a d i a l growth was most rapid between 15 and 1+5 years. The l a t t e r period may represent a time of peak thinning for t h i s p a r t i c u l a r stand. - 182 -During the period of rapid population growth the change i n numbers of weevils r e f l e c t s more of an increase i n i n t e n s i t y (weevils per tree) than an increase i n absolute numbers. The increasing tree size and reduction i n stems- per acre have the effect of making populations more highly aggregated. A maximum peak of weevil abundance i n the 65-70-year old stand was suggested at the age of about 45 years. However, the. method of dating weevil scars did not take into account certain changes i n attack pattern during the growth of the stand and with increasing stem diameter. Evidence was presented which indicated an expansion of the l a r v a l universe to include portions of the roots as tree size increases. The error' involved i n estimating numbers of scars may therefore be highest for measurements of the past 15-20 years, due to an increasing number of feeding sites on roots. Some scars on the lower portion of the c o l l a r may also have been missed. The sharp decline indicated i n Figure 33 since the stand age of 46 years i s more apt to be a l e v e l l i n g - o f f or a more gradual decline. I t i s noteworthy that, basal area of f u l l y stocked, pine stands attains a maximum at 60 years of age (Smithers 1957). This supports the view that population i n t e n s i t y levels may not increase s i g n i f i c a n t l y beyond th i s age. From an examination of the- attack patterns i n a l l sampled areas i t i s possible to reconstruct a schematic sequence of events which describes the development of H. warreni populations during the normal growth of lodgepole pine stands. This pattern may be considered t y p i c a l of good growing site s i n the Lower F o o t h i l l s Section of Alberta. Adult weevils immigrate i n i t i a l l y into pine stands 8-10-years old. Their attack pattern - 183 -remains e s s e n t i a l l y the same- throughout stand growth; the order of preference f o r o v i p o s i t i o n i s on dominant, co-dominant, intermediate and suppressed t r e e s i n t h a t order. P o p u l a t i o n build-up appears to be slow f o r the f i r s t few generations. Presumably t h i s i s p a r t l y dependent upon the d e n s i t y of immigrating a d u l t s , and p a r t l y due to s u r v i v a l i n the new h a b i t a t . The r a t e of advance i n t o the stand i s at l e a s t 3 5 - ^ 5 f e e t per year on average s i t e s . During the e a r l y years of a t t a c k ; i . e . , up to the age of 20-25 years, there may be up to f i v e percent m o r t a l i t y of the l a r g e r t r e e s caused d i r e c t l y by l a r v a l g i r d l i n g . Only s c a t t e r e d m o r t a l i t y may occur t h e r e a f t e r . The a t t a c k d e n s i t y on most of the young tr e e s may not exceed 1-2 larvae per . t r e e . As the t r e e grows, so a l s o does the r a t e of o v i p o s i t i o n and the l a r v a l universe increases i n area. Dominant tr e e s approaching m a t u r i t y may have an a t t a c k d e n s i t y of 20 or more lar v a e each. Between.the p e r i o d of stand ages 10 years and maturity, stand d e n s i t y may be reduced from over 5000 stems per acre to 500 stems per acre.• Thus, w h i l e w e e v i l p o p u l a t i o n i n t e n s i t y increases w i t h stand age, absolute numbers of weevils may remain r e l a t i v e l y constant at some l e v e l between 500 and 1500 weevils per acre. I t i s expected t h a t , w i t h i n t h i s range, annual f l u c t u a t i o n s would normally occur. F o l l o w i n g the i n i t i a l slow phase of p o p u l a t i o n build-up there i s a r a p i d increase from about the age of 30 years to 45 years, t h e r e a f t e r there i s a l e v e l l i n g - o f f . As stand m a t u r i t y i s reached near 80 years a slow d e c l i n e can be expected i n p o p u l a t i o n i n t e n s i t y and i n absolute numbers. The sampling system used appears to have been adequate f o r showing general trends i n abundance, f o r d e s c r i b i n g p o p u l a t i o n s t r u c t u r e and i n d e f i n i n g w e e v i l h a b i t a t r e l a t i o n s h i p s . However, some refinements are p o s s i b l e , - 184 -i f the system i s to be used for detailed population studies. Southwood (1966) has indicated that a s t r a t i f i e d random sample i s recommended for most ecological work i n that i t provides best representation of the t o t a l area to be sampled. Es s e n t i a l l y , t h i s condition was p a r t i a l l y f u l f i l l e d i n the design used within the 65-70-year old stands of plots 1 to 7 . In each plot the block was a minimum sized area.in which a fixed number of trees were randomly chosen. In even-aged pine stands, which i s the most common situ a t i o n i n the Alberta f o o t h i l l s , the i n d i v i d u a l tree i s probably the simplest to handle as a basic sampling un i t . Each tree can be regarded as a complete b i o l o g i c a l unit i n i t s e l f . Additionally, weevil numbers expressed on a per tree basis can be related d i r e c t l y to absolute numbers, or to degree of tree damage. Contagion i n the weevil habitat appeared to be due to two things when the tree was taken as the sampling unit. I t was due to the adult weevil recognizing large trees for greater oviposition- as compared to small trees. I t was also due to the gradient of tree sizes i n natural pine stands. These two characteristics are interrelated, the former being a determinant of oviposition s i t e s , while, the l a t t e r provides the source of attraction. I t i s suggested that i n pine plantations where l i t t l e gradient of tree size exists a more random weevil d i s t r i b u t i o n might be expected since the trees should be attacked with almost equal p r o b a b i l i t y and i n t e n s i t y . The degree of contagion caused some s t a t i s t i c a l problems i n the analysis of weevil populations from i n d i v i d u a l trees. In plots 1 to 10 the high proportion of trees with zero weevil counts (up to 75 percent for low population levels) added the problem of selecting a suitable transformation. - 185 -While Taylor's power law suggested that a logarithmic scale would be adequate (b = 1.92) this did not provide normality to the data. However, when weevil numbers were pooled from groups of f i v e trees, then transformed to a logarithmic scale, the requirements of normality and s t a b i l i z a t i o n of variance were f u l f i l l e d . From th i s i t appears that a s t r a t i f i e d random sampling system i n which clusters of f i v e trees are randomly selected might offer the best approach to detailed sampling. Because of the lower weevil densities per tree i n the regeneration plots the cluster size may have to be increased considerably. The number of such cluster units required to give a chosen degree of precision was not established. One alternative to the use of the tree as the sampling unit might be to equate weevil numbers per tree to a common unit area of the tree surface, measured from the t o t a l l a r v a l feeding universe. While t h i s would not decrease the number of zero counts, i t might relate more d i r e c t l y to the available space for oviposition. The studies of the relationship between tree size and weevil numbers within stands indicated that a l l trees do not have equal p r o b a b i l i t y of attack. However, the actual measurement of the r o o t - c o l l a r surface area available to the weevil would pose several problems. Surface area estimates may vary with tree size, with rooting patterns, with duff depth and probably with tree density. Special techniques would have to be devised for estimating surface area. The method of sample tree selection for plots 1 to 1 allowed a residu a l of 40 -50 percent of unsampled trees at the end of the four annual samples. Further.dissruption of the l a r v a l and adult habitat may interfere - 186 -with the normal pattern of weevil d i s t r i b u t i o n , and may have the effect of concentrating the population upon the residual non-sampled trees. I f weevil populations are to be followed over a greater period of time a s t r a t i f i e d sampling system using a plot size which would allow more than 40-50 percent of unsampled trees would be desirable. Since weevil numbers were found to be d i r e c t l y related to percentage of trees with fresh attacks, direct application of t h i s relationship could be made use of i n designing a sampling system for general surveys of weevil abundance and damage appraisals. The system would use the tree as the basic sampling unit, and each tree would require a minimum amount of e f f o r t to determine the presence or absence of fresh weevil attacks. When the f i r s t l i v e weevil i s located the sampler would then proceed to the next tree. Each freshly attacked tree would be scored . p o s i t i v e l y . The t o t a l percentage of trees with fresh attacks would provide an estimate of population density, or be an indication of p o t e n t i a l and actual damage. By t h i s system stands with high population levels would require less time to assess than would stands with low populations since ron the whole,,trees i n the former category would, require less searching than trees i n the l a t t e r . The present studies were i n agreement with Stark's finding ( l959 a ) that a l l stages of l a r v a l development could be found throughout the summer, and that egg laying also occurred during most of the summer period. Since the l i f e cycle i s not synchronized, therefore, i t i s questionable whether the l i f e table approach would provide r e l i a b l e information regarding a mortality with age relationship. Larvae born i n June, for example, may be confronted with different mortality factors than larvae born i n August. - 187 -Thus, while they may be of the same age they are separated hy different b i o l o g i c a l events. The mortality of eggs may be s i m i l a r l y d i f f i c u l t ' to assess. The frequency d i s t r i b u t i o n of l a r v a l head capsule widths did not show d i s t i n c t peaks beyond the t h i r d instar, indicating the u n r e l i a b i l i t y of such data i n determining t o t a l numbers of instars. Seven instars were recorded from a r t i f i c i a l rearings of larvae by Warren (1960a) , while Stark (1959b) defined s i x on the basis of head capsule measurements. Similar problems have been encountered i n the determination of instars of o.ther Hylobius species. Measurements of H. r a d i c i s f i e l d collected larvae.provided only an indication of the number of instars, while f i v e , s i x and seven were reported for a r t i f i c i a l l y reared material (Finnegan 1962a). Five and s i x instars were recorded for H. pales, but the smallest larvae i n the f i f t h instar group generally transformed to a s i x t h instar before pupating (Finnegan 1959)• . . • . In Europe, H. abietis develops through at least f i v e instars and certain- differences exist between pine and spruce reared material (Nordic Forest Entomologists' Research Group 1962). Five instars were noted for H. piceus (Scherf 1964). I t i s possible that the number of instars of H. warreni may vary from f i v e to seven. The extent of mortality and the factors involved of f i r s t instar larvae could not be'determined since the larvae were always located within small g a l l e r i e s of the outer phloem. The s i t e of oviposition varied from within the adjacent s o i l to frass-covered niches i n the bark. Some mortality due to predation can be expected between the period of hatch and establishment i n the bark, especially when the oviposition s i t e i s external to the bark. - 188 -Once feeding began the larvae were usually confronted with fresh r e s i n flow which they used continuously as a protective covering. There appeared to be l i t t l e evidence that excessive r e s i n flow could be a mortality factor, except i n d i r e c t l y by trapping moisture. Studies of the feeding behavior indicated that young larvae adjusted th e i r feeding depth i n the phloem as they increased i n size. This may be an adaptive feature for survival. Throughout i t s development the larva- destroys a large quantity of inner phloem and cambial tissues (9+ inches of g a l l e r y ) , and much of t h i s i s used d i r e c t l y as food. Where patches of dead phloem and cambium appear as a r e s u l t of feeding, i t can be assumed that, this represents an actual destruction of feeding area to succeeding larvae. The feeding pattern of l a t e r larvae may be altered depending upon the; .extent of previous damage. I t has also been noted that large accumulations of resin-soaked s o i l , up to 3~h inches thick, occur adjacent to the wound areas of cs.ome trees. This material becomes s u f f i c i e n t l y hard to be impenetrable by the adult weevil, as w e l l as to early instar larvae. Thus the oviposition pattern and l a r v a l feeding patterns can be affected by d i r e c t loss of cambial and phloem areas, and to some degree by the hardened masses of resin-soaked s o i l . In addition, the behavior of the adult can be affected through an increase i n time spent i n searching out oviposition sites as damage int e n s i t y increases. Although the sloughing-off process of bark scales, tree growth and the healing process combined would tend to reduce damaged areas i n time, the implication i s that weevil numbers become p a r t l y a function of attack density and of the frequency of re-attack. I f the tree i s heavily attacked during one p a r t i c u l a r period t h i s would immediately influence the pattern of re-attack - 189 -for several subsequent years. This provides one explanation why many trees of a l l sizes i n mature stands had no weevils, while adjacent trees had many. In most sample p l o t areas the percentage of trees with current attacks did not exceed 55. Similar findings were obtained by Stark (1959a). The measurements of bark thickness and r e s i n cavity s t a t i s t i c s showed that the nature of the l a r v a l universe between the l a t e r a l roots and main stem i s t r a n s i t i o n a l i n these microhabitat characteristics. There' appear to be d i s t i n c t advantages for egg deposition and i n i t i a l feeding to occur on root bases since there i s minimal contact with r e s i n cavities as compared to the tree stem base. Within the c o l l a r zone bark thickness i s maximal; t h i s provides a maximum food supply for larvae and may require about the least amount of mechanical ef f o r t to obtain i t . In a l l sample plots the highest incidence of mortality occurred:', i n the prepupal, pupal and teneral stages. However, these higher values may r e f l e c t the ease with which these stationary stages were located. Mort a l i t y of eggs and adults, could not be assessed quantitatively inasmuch as only some of the factors were i d e n t i f i e d . Pupae were found very susceptible to moisture i n the chamber. Other workers have observed similar findings for H. r a d i c i s (Finnegan•1962a; M i l l e r s 1965). M i l l e r s also demonstrated that submersion of H. r a d i c i s eggs i n water for more than a day caused mortality, and that contact with free water-could prevent development. The eggs of H. warreni appeared to be s l i g h t l y more resistent to moisture. Rearing studies suggested that egg hatch was most successful i n a saturated atmosphere. In the prepupal and pupal stages the two main parasites, B. bassiana ~ 190 -and D. tuberculatus tuberculatus may tend to increase i n response to increasing weevil populations but observations were too few to confirm t h i s . Highest numbers of the Hymenoptera parasite were recorded i n 1963 i n plots 1 to 5 . With the exceptions of plots 1 to 5, AB, I963 and 7, 1962, the incidence of mortality of entire populations was less than f i v e percent. The higher percentage i n the cut stumps of 1963 (plots 1 - 5 , AB) i s reasonable because of the drast i c changes effected through clearcutting. In plot 7, I962, however, mortality i n the pupal c e l l s was especially high i n r e l a t i o n to the o v e r a l l population l e v e l . This may have been related to the predominantly moss forest floo r cover and to the r e l a t i v e l y high stand density. Several authors, including Benham and Miranda (1953) and MacLeod (1954) have maintained that B. bassiana attacks a large variety of insect hosts, and the p o s s i b i l i t y of i t s use as a controlling agent has been described (Angus i 9 6 0 ) . In Europe an integrated method-of control for H. abi e t i s has been described using a weak insecticide (DTHP) with a suspension of B. bassiana spores (Samsinakova and Novak 1967)• L i t t l e i s apparently known of the habits of the l a r v a l stage of Laphriinae Diptera. According to Imms (1957) they inhabit s o i l , wood and leafi mould and are either predacious or scavenging. Elton et... a l . (1964) provided evidence that certain species inhabiting cut pine stumps i n Holland were predacious on larvae of Hylobius a b i e t i s . The r e l a t i v e l y large numbers of dead adults found at tree bases (Table XXVI) may suggest that they died from old age or from i n t e r n a l parasites. However, only one of the 36 dissected females was observed with i 1 - 191 -i n t e r n a l nematodes. Dr. Ruhm (personal communication) stated that four dif f e r e n t species of nematodes are associated with Hylobius a b i e t i s . Ro effects of the attacked mites (Hericia sp.) upon the longevity or fecundity of weevils were observed. However, there i s evidence that mites cause s t e r i l i t y i n the Corixid, Cenocorixa b i f i d a Hung. ( J . Simpson, n personal communication), and the p o s s i b i l i t y of a similar effect i n the weevil should not be overlooked. Although no evidence of adult weevil predation by shrews was detected from stomach content examinations, Warren (personal communication) noted that S. cinereus cinereus i n c a p t i v i t y r e adily accepted adult H. warreni as food. I t i s possible, therefore, that they db i n fact prey upon the weevil i n the natural habitat. However, the sampling procedure for c o l l e c t i n g shrews may have f a i l e d to detect predation for two reasons. F i r s t l y , adult weevil locomotion on the duff surface and up tree stems was greatest between the hours of 10:00 p.m. and 1:00a.m., and i t i s during t h i s time that greatest predation should be anticipated. Since shrews were collected i n the morning between 9 ; 0 0 - 10:00 a.m., the time lapse would be s u f f i c i e n t for complete digestion. Secondly,, since adult weevil populations appeared to be very low, the prey-capture behavior and diet of shrews were l i k e l y conditioned to the more abundant insect species such as carabid beetles. This was evident from the stomach content examinations. The numbers of adult weevils collected by the different methods show few d i s t i n c t patterns for interpretation. Newly developed males and females occurred i n about equal numbers and a 1 : 1 r a t i o was also described by Stark (1959a) . I t was apparent that -the two sexes differed i n behavior - 192 -as evidenced by the greater numbers of males collected from border trees as compared to trees within stands. Several reasons may be postulated to explain the differences. Females may tend to be more active than males i n l a t e r a l dispersion as w e l l as i n feeding. Evidence for t h i s i s suggested by the greater numbers of females capture! i n plots A and B. The fact that males were found nearer to the duff surface than females may account for the higher numbers by the tree base-duff search method, but does not account for the higher numbers caught i n traps on border trees. A second reason may be that females are more sensitive to moisture requirements i n the r o o t - c o l l a r environment, and hence were more active i n locating these areas. This i s also a reasonable assumption since the bases of border s t r i p trees appeared considerably dryer than tree bases within the stand. Warren (1956b) suggested that adults may seek out oviposition sites i n the environment best adapted to t h e i r requirements. A t h i r d p o s s i b i l i t y may be that mortality of females was higher on the border trees than of males,.although there appears to be no direct evidence for t h i s . Another p o s s i b i l i t y may be that males disperse more l a t e r a l l y than females. However, the evidence from trapping and behavior studies tend to favor the f i r s t two postulates. As indicated by the trap method of c o l l e c t i o n i n plots A and B (Table XXVI) females were more than twice as abundant as males during the 1964 and 1965 periods, but i n 1966 they were almost equally abundant. Data i n Table XXVII suggests two alternative explanations. The rate of capture indicated that the male population i n the plots remained constant during the three year trapping period, and that the change i n sex r a t i o i n I966 was proportional to the lower capture rate of females i n 1966. I t was - 193 -suggested that a d i f f e r e n t i a l mortality rate accounted for the apparent-decline i n the female catch rate, or that- t h i s reduction was brought about by a change i n behavior pattern. The fi r s t - explanation appears most-plausible since the age structure of adults should remain r e l a t i v e l y constant i n time. In contrast, a drastic change i n behavior pattern, as a res u l t of maturity, or immaturity does not appear l i k e l y . Further studies are required to c l a r i f y the differences i n d i s t r i b u t i o n and abundance of the sexes within stands. When the percentages of captures, 1+ times (Table XXVIl), are pooled for d i f f e r e n t years and plots, but- separately for the sexes, the values indicate that males and females were recaptured at about the same rate (females kl.2ff0 and males kk.1%). This suggests that females were i n fact more abundant than males i n plots A and B, and that t h e i r tree climbing behavior was sim i l a r . The data describing the numbers of adult-captures i n r e l a t i o n to tree size-support t h i s idea. 'The tree size relationship also indicates that i t i s the selection pattern of trees by females which accounts largely .for the subsequent d i s t r i b u t i o n pattern of l a r v a l , pupal and teneral numbers. The interpretation of the graphs describing rate of dispersion implies that after one night of t r a v e l l i n g an adult can be expected about 8 feet, on the average, from i t s tree of o r i g i n . After two nights i t can be expected about 12 feet, after 10 nights about 20 feet and after 20 nights about ko feet. While t h i s suggests a very l o c a l pattern of t e r r e s t r i a l movement i t i s d i f f i c u l t to ascribe b i o l o g i c a l meaning to the pattern. When leaving a tree of o r i g i n the d i r e c t i o n a l response was random, at- least - 19k -i n i t i a l l y , and movement tended to be uni d i r e c t i o n a l . In locating host trees, however, there was evidence that they do so p a r t l y by v i s i o n . In th i s respect the correlation of weevil movement, during one night's t r a v e l , with average distance between trees i s reasonable.. The studies of weevil reproduction have demonstrated a r e l a t i v e l y low fecundity for H. warreni. Studies by other authors generally agree with t h i s . Warren (1955) noted that the maximum number of eggs l a i d by a single. H. warreni female during a summer period was 33, while Stark (1959a) observed nine eggs. Warren (1956a) also observed that the highest oviposition period occurred during.May, June and July. He obtained percentage hatches which varied from 7 . 6 to 70 .0 for dif f e r e n t years. Several authors have studied the oviposition habits of other Hylobius species. Finnegan (1962a) reported up to ko eggs per female per season for H. r a d i c i s , but noted that there was wide v a r i a t i o n among them. He obtained an average of 17 .5 and 14 .2 eggs per female during the f i r s t and second years of rearing respectively. His findings for H. pales (Finnegan 1959) were s l i g h t l y higher than for H. r a d i c i s for f i r s t and second summer rearings. Shaffner and Mclntyre (l9kk) and M i l l e r s (1965) obtained maximums of 6k and 67 eggs respectively per female H. r a d i c i s from laboratory rearings. A maximum of 33 eggs for one female was also recorded for H. rhizophagus by M i l l e r s (Kearby I965) , while Heqvist (1957) obtained 10 eggs per female from laboratory rearings of H. piceus. Hylobius abietis and H. cribropennis showed higher egg p r o d u c t i v i t i e s ; i e . , 60-80 eggs per female (Scherf 1964) and 70-80 per female per season (Matsuzawa et. a l . I963) respectively for the two species. The egg laying period of H. r a d i c i s appears similar to that of H. - 195 -warreni. Finnegan (1962a) and M i l l e r s (1965) both observed oviposition of H. ra d i c i s from May to September. These authors also observed an egg laying rate of 1-1+ eggs per female per day; similar observations were noted for H. cribropennis (Matsuzawa et. a l . 1963). The habit of constructing a special niche i n the bark for placement of eggs and subsequently covering them over with excreta, appears to be common to several Hylobius species. The female H. r a d i c i s excavates a small chamber i n the inner bark i n which one egg i s usually placed ( M i l l e r s 1965). The cavity i s then covered with t i g h t l y packed excrement. A similar habit was described for H. cribropennis (Matsuzawa et.. a l . I963) • This appears to be a special adaptive feature which confers safety on the egg from excess moisture and from predation during the r e l a t i v e l y long developmental period of the embryo. Survival i s ad d i t i o n a l l y enhanced through the habit of depositing eggs singly i n any pa r t i c u l a r laying s i t e . The attempts made to estimate t o t a l summer egg productivity for H. warreni showed considerable v a r i a b i l i t y . While 36 eggs may represent a pot e n t i a l maximum per female, the average was only'.12.2 eggs per female. This i s about half the value obtained (2k.3 eggs) by calculating from 103 possible egg laying days. This implies that less than half t h i s number of days may be suitable for oviposition i n the f i e l d . Data presented i n Table XXX tend to support t h i s , .where only 1+.00-5-37 eggs per female were estimated i n a natural habitat si t u a t i o n . These values should be considered minimal, however, since eggs were d i f f i c u l t to locate. Low night temperatures, periods of drought and periods of heavy r a i n f a l l may contribute to periods of non-laying a c t i v i t y . - 196 -The long pre-oviposition period of about one year suggested from rearing H. warreni i n plots C and D i s uncommon i n the insect world. However, Matsuzawa et. a l . (1963) also described a pre-oviposition period of two to three months for H. cribropennis. This period would seem to be a weak l i n k i n the l i f e history since. H. warreni females appeared to carry on a l l l i f e functions except egg laying (Tables XXVIII and XXX) during the i r f i r s t year. The percentage of eggs i n niches may provide an indication of s u i t a b i l i t y of microhabitat conditions i n the roo t - c o l l a r zone. Under the most favorable conditions observed i n plots C and D (Table XXX), and by experimentation (Table XXXl), the percentages of eggs i n niches were a l l above 70. While no studies were undertaken to compare su r v i v a l of eggs and f i r s t instar larvae i n niches versus other egg laying s i t e s , the niche would seem to provide maximum protection. Not only are eggs maintained i n a r e l a t i v e l y constant and stable environment i n the niche but the newly emerged larva i s provided with an immediate and protected source of food. I t i s thus free from the r i s k of predation during translocation from within the adjacent s o i l to the bark environment. Unfavorability i n the microenvironment for oviposition may be c r i t i c a l when the duff layer i s shallow and dry (Table XXX, plot D, 1966). This condition was improved i n plot C by adding sphagnum mosses around tree bases. A duff layer which i s extremely moist may also have an i n h i b i t i n g effect on oviposition. This was suggested i n cages 21-30 (Table XXXl) where the moisture l e v e l may have been excessive. The lower temperature conditions of these cages l i k e l y had the effect of reducing the rate .of oviposition but should not have effected the position of egg laying s i t e s . - 197 -During the rearing experiments described i n Table XXXI some error i n fecundity may have been due to the timing of each set of cages. I t was shown that oviposition attained a maximum i n early July. Cages which were established after t h i s date may r e f l e c t the reduced laying a c t i v i t y period. The trapping experiments i n plots A, B, C and D suggested that weevils were most active i n dispersal i n June as indicated by numbers of captures per day. I t was not established, however, whether t h i s represents a period of active migration. Feeding requirements would l i k e l y be highest during t h i s period of maximum dispersal. In addition, mating a c t i v i t y was most common during the months of June and July (table XXXII). Thus the overa seasonal trend of activity,, including egg laying, slackens after July. The most active period coincides with the month of June when temperature and moisture conditions i n the Alberta f o o t h i l l s are l i k e l y optimal for the weevil. High temperatures and low-moisture are characteristic of July and August. Studies of night time temperatures i n plots C and D showed that few nights i n May are suitable for adult a c t i v i t y since .the temperatures f a l l below 40 °F. by 11:00 p.m. on most nights'. Studies of the feeding habits of H. warreni generally agree with observations by Warren (1956b). However, i n contrast to his studies, there was l i t t l e evidence that the adults fed upon the needles of lodgepole pine. The maxima of feeding scars shown i n Figure 70 may have been due to a sexual difference, with females preferring the upper crown areas and males the lower crown areas. Another p o s s i b i l i t y i s that f a l l i n g temperature or wind i n the evening may have r e s t r i c t e d t h e i r movement to the lower canopy The impact of weevil damage to i t s lodgepole pine host has - 198 -implications i n the survival, growth and development of i n d i v i d u a l trees and upon the stand as a whole. Sampling studies i n infested stands indicated that up to 100 percent of trees may show evidence of l a r v a l feeding, but the degree of damage varies widely among trees within the same stand. Warren (1956b) has adequately assessed l a r v a l feeding damage on white spruce to show i t s cumulative characteristics with each successive attack. Stark (1959b), however, indicated that the "Damage Index" rati n g method used by Warren, based upon degree of g i r d l i n g of c o l l a r and roots, was unsatisfactory i n expressing tree injury to lodgepole pine. He suggested that some modification was necessary for the pine. According to Kramer and Kozlowski (1962) death by g i r d l i n g i s probably caused by desiccation r e s u l t i n g from i n j u r y to the root system through lack of carbohydrates. Mortality was r a r e l y observed, however, i n trees over three inches i n diameter, or after the age of 30 years. Trees smaller than this showed less resistance, probably because fewer larvae were required to do an amount of damage equivalent to that on larger trees. In addition, the pattern of l a r v a l feeding and gallery orientation was shown to d i f f e r between young and old trees. With increasing tree size weevil damage becomes more extensive down the roots and this may tend to reduce the impact of damage to the tree. Most of these feeding sites occur on the upper and l a t e r a l aspects of the root, and only occasionally are they present on v e r t i c a l roots and sinkers. Horton (1958) showed that root sinkers developed from the underside of major l a t e r a l roots and from the taproot, usually before the polewood stage (about kO years). He suggested that the v e r t i c a l roots function s i g n i f i c a n t l y i n anchorage and absorption. Thus the change i n developmental pattern of root - 199 -structure as the tree passes from the sapling stage may confer resistance against the wounding effects of larvae. The claim that weevil damage i s cumulative with each successive attack may not be s t r i c t l y true. Some allowance i s needed for tree growth characteristics and the natural healing process. Damage assessment values do not remain s t a t i c i n time as long as the tree continues active growth. Total damaged areas may decrease i f no further wounding occurs. Therefore, damage i s cumulative as i t relates to the time of measurement, and any subsequent measurements might give higher or lower values. While the results of growth measurements i n the two young pine stands indicated growth losses i n the v e r t i c a l and horizontal dimensions of the tree, the data can be interpolated into the stand as a whole only i n a limited way. A small percentage of trees i n a stand ( i . e . , less than 10 percent) may have g i r d l i n g damage equal to or exceeding 45 -50 percent of the root c o l l a r circumference. Trees with this amount can occur i n the dominant, co-dominant and intermediate categories. However, since dominant and co-dominant trees receive most of the i n i t i a l attacks t o t a l growth loss over the developmental period of the stand may be considerable, especially on the better s i t e s . This assumes, of course, that the degree of tree height reduction i s comparable for a l l ages or sizes of trees having an equivalent amount of p a r t i a l g i r d l i n g . Some sampling results of Warren (1956b) and Stark ( l 9 5 9 a ) i n mature pine near Strachan, Alberta i n 1954 and i n 1957 respectively, indicated average damage indices of the order 4 . 5 and 4 . 2 . This may be equivalent to 5-25 percent g i r d l i n g of roots and c o l l a r regions for the stand as a whole. The 1966 examinations of the same stand (plot 10) revealed that many trees - 200 -had one or more major l a t e r a l roots k i l l e d from weevil feeding. While 5 -25 percent g i r d l i n g may be an i n s u f f i c i e n t quantity to cause a detectable growth reduction to a l l trees i n the stand, a small proportion may be seriously affected. The o v e r a l l effect would not appear severe enough,to cause a notable change i n stand structure, such as a s h i f t i n crown levels of d i f f e r e n t sized trees or large stand openings. On the other hand, any tree mortality caused d i r e c t l y or i n d i r e c t l y by weevil feeding would affect tree spacing and competition. On good pine sites which maintain weevil populations over long periods of time the t o t a l impact of the weevil l i k e l y plays a role i n the hastening of stand decadence by contributing to a general o v e r a l l reduction i n growth, by allowing entry of root and stem decay organisms, by reducing the effective root system and by making trees r more prone to windthrow. Evidence i n support of th i s comes from several workers, including Nordin (1956) , Warren (1956c) and Stark (1959b). The implication of the t o t a l impact i s that natural successional changes may proceed at a faster rate than normal with the aid of the weevil. I t i s apparent that several factors are responsible for the spacial v a r i a b i l i t y i n abundance of weevils i n forested areas. The weevil tolerates pine forests of nearly a l l ages growing on a variety of sites from dry to wet. Their greatest abundance coincides with the medium to moist s i t e s , and usually these are characteristic of high quality s i t e s . Within these stands the weevil i s distributed according to four main stand variables^ stand maturity, tree size, tree density and duff depth. Fav o r a b i l i t y of the microhabitat of the weevil i s inherent largely i n these four variables. For example, stand maturity, tree size and duff depth dictate the number of eggs which can be l a i d and the amount of space available for l a r v a l feeding. - 201 -Tree density regulates to a degree host and mate finding e f f i c i e n c y and has interactions with a l l other stand variables. In addition, the rate and degree of forest succession, as w e l l as habitat conditions of moisture and temperature, are influenced by stand density. The quality and quantity of duff relates d i r e c t l y to s p e c i f i c requirements of the weevil, affecting adult dispersal, .oviposition, hatchability, development of larvae and surv i v a l of a l l stages. In essence the combination of these four stand variables accounts largely for the different levels of abundance i n diff e r e n t stands. Providing that the four stand variables allow successful survival and growth of a weevil population, a f i f t h factor comes into play. This factor i s inherent i n the behavior patterns of the weevil. The female was found to deposit her eggs according to a tree size relationship. This suggested some regulatory mechanism i n d i s t r i b u t i n g her eggs according to a root and root c o l l a r surface area basis. Where previous l a r v a l wounds occur the space available for new oviposition s i t e s , as w e l l as l a r v a l feeding areas are reduced accordingly, so that weevil numbers become pa r t l y a function of host attack density and the frequency of re-attack. This idea derives support from the fact that damage i s cumulative and that up to 100 percent of trees i n a stand may show old attacks. The rate of tree growth, rate of wound healing and natural thinning processes inturn influence attack density and the frequency of re-attack. This implies that the o v e r a l l numerical r e s t r a i n t and s t a b i l i t y of the weevil i s accomplished largely through i t s own behavior patterns. The. special adaptations of the weevil which provide the mechanisms through which i t s v a r i a b i l i t y i n abundance, numerical r e s t r a i n t and s t a b i l i t y - 202 -are made possible are many. These include a low fecundity rate, a long pre-oviposition period, a l i f e cycle of up to fi v e years long or more, a reduced period of a c t i v i t y i n the adult stage and slow means of dispersal. I t s f l i g h t l e s s condition 'and nocturnal habits s i g n i f i c a n t l y reduce the period and rate of a c t i v i t y . The habit of climbing trees may have survival value since i t reduces the p o s s i b i l i t y of predation. Placement of eggs i n special niches and the construction of the pupal chamber may enhance sur v i v a l . The long period of embryonic development and establishment of early instar larvae require the special protection of the bark niche. In the l a r v a l stage a major adaptation i s the a b i l i t y to withstand r e s i n flow of the most vigorous trees, and to u t i l i z e t his material: for i t s own protection. The relationships of weevil numbers with forest conditions ..in the Alberta f o o t h i l l s suggest that there exists an ecological feedback which l i m i t s the abundance of the weevil i n stands. On the whole, the weevil does not appear to increase at a rate, or i n f l i c t damage to.an extent greater than the normal recovery rate of i t s host. In theory, extensive host mortality and low density stands would tend to reduce host finding' a b i l i t y , and thereby lower the rate of increase. There appears strong selective advantage to attack most heavily the largest and most vigorous trees i n a stand since t h i s allows maximum population levels to be maintained, and at a tolerance l e v e l that allows l i t t l e or no tree mortality. For the same reason the most productive growing sites of lodgepole pine appear to have the p o t e n t i a l to support and maintain the greatest levels of abundance. The o v e r a l l studies of the weevil suggest several avenues for implementation of c u l t u r a l control measures against the weevil. I n i t i a l l y , - 203 -the decision to carry out control can be based upon an assessment of weevil abundance i n mature stands p r i o r to cutting. This would help to establish a s i t e p o t e n t i a l rati n g of future weevil a c t i v i t y . The assessment can be i done by the sampling technique described i n Figure .33 and Table XXIII. Stands showing population levels i n the "high" category (62 .0 percent or more of trees with fresh attacks, or an average of 2 .50 or more weevils per tree) may be considered a reasonable c r i t e r i o n for i n i t i a t i n g control measures. Various s i t e factors may also be used to recognize high p r i o r i t y s i t e s . These include stands having a predominance of pine, a density of 300-600 stems per acre, good growth characteristics, r i c h f l o r a l complex including a large proportion of mosses .and a duff depth of 5 - 7 inches. In general, concern for the weevil i n stands with these characteristics need apply only i n the Lower F o o t h i l l s Section of Alberta. Following the establishment of a high population index i n a mature stand most attention should be directed toward keeping out weevils from regeneration pine established after clearcutting. Because of the persistence of weevils i n stands i t i s not f e l t economically j u s t i f i e d to attempt control once populations become w e l l established, at least i n forests u t i l i z e d for pulpwood or related uses. In infested mature stands clearcutting destroys a large portion of the weevil population (estimated 67 percent), but larvae can s t i l l complete thei r development one and two years after tree removal. The newly developed adults from cut stumps pose a problem to any advanced regeneration pine or uncut trees. Since they are long-lived the adults are also of concern i n the timing of i n i t i a t i n g the new stand and i n the clearcutting of residual s t r i p s or blocks. For t h i s reason a complete - 204 -clearcut of the stand, including any advanced regeneration pine and white spruce would be most effective i n reducing weevil abundance. S c a r i f i c a t i o n treatment applied soon after cutting would l i k e l y hasten mortality of larvae and pupae i n the cut stumps. Where pine areas are clearcut i n alternate s t r i p s or i n block patterns, the residu a l s t r i p s and blocks should not be retained longer than 2 - 4 years. This period would allow s u f f i c i e n t time for natural regeneration or planting on the cut areas and would decrease the change of re-invasion into the young stand. I t would also reduce the chance of population b u i l d -up i n the border trees. The 2 - 4 year period takes into account su r v i v a l of larvae i n the cut stumps as w e l l as adult longevity. . Since the rate of adult dispersal into young stands may be 35 feet or more per year there i s merit i n increasing the size of area of clearcutting. Immigration of weevils into young stands may be retarded i n i t i a l l y i n overly dense stands. However, since dense stands•can lead to stagnation (Smithers 1962) an early pre-commercial thinning might-, favor a build-up i n population intensity. By concentrating the weevils on the residual trees, and by creating a stand si t u a t i o n analogous to a plantation, considerable tree mortality and growth loss could r e s u l t . The encouragement of an aspen intermixture or an underplanting of black spruce would tend to favor a decrease i n the rate of population build-up. Within stands Warren (1956c) postulated that H. warreni may be controlled by removing the humus from the v i c i n i t y of the root c o l l a r and basal portions of major roots. He suggested that the humus layer provided protection to the insect's habitat by maintaining a high humidity. The - 205 -present studies agree with t h i s but suggest that the main effect of duff removal i s i n reducing the area available for successful oviposition. Studies by Wilson (1967) demonstrated that removal of lower branches and tree base duff material, and the scraping of surface s o i l around the tree base reduced H. r a d i c i s l a r v a l populations to below an economic l e v e l , at least for the f i r s t year. Wilson suggested that the greater exposure to l i g h t or heat, or both, at the tree base created an unfavorable habitat for the adult weevil. SUMMARY Ecological studies of the root weevil, Hylobius warreni Wood were conducted i n lodgepole pine forests i n Alberta. The main objective was to evaluate this insect pest i n terms of i t s p o t e n t i a l destructiveness to forests. Answers to two ecological questions were.sought: what factors are responsible for the weevil's s p a t i a l v a r i a b i l i t y i n abundance i n forests and what factors are responsible for i t s apparent numerical r e s t r a i n t and s t a b i l i t y . In the f i r s t stage of study the geographical range of the insect was mapped with p a r t i c u l a r emphasis upon the d i s t r i b u t i o n a l range of i t s pine host. In the second stage plot areas within a variety of pine stand conditions were sampled to ascertain patterns of weevil abundance, t h e i r change with time and the i r correlation with stand conditions. The physical nature of the weevil habitat was analysed i n the main study areas to provide a basis for comparison with other infested stands. This included vegetation, - 206 -s o i l , climate and topographic characteristics. Weevil abundance was followed i n 7, 3-acre plot areas over 2 - , 3 - and 5-year,.periods. Thirteen additional plots were sampled for weevil numbers and attack incidence. Levels of abundance were related to stand maturity, tree size, tree density and duff depth. Clearcutting treatment was applied to some of the plots to assess t h i s practice as a method of control, and for i t s effects upon weevil su r v i v a l . Weevil numbers and the attack d i s t r i b u t i o n upon the host were described from a variety of stands, a few years old to-mature, to i l l u s t r a t e the chronological patterns of change with normal stand development. Related information was collected from mature attacked trees through an analysis of dated l a r v a l scars. Stand s u s c e p t i b i l i t y was analysed i n a variety of young stands by scar dating, and by determinations of the age and size of trees when i n i t i a l attacks occurred. The rate of weevil spread within stands was estimated from plot areas extended into young stands from boundary trees which supported reservoir populations. Their selection of hosts and attack density patterns were related to stand maturity. A t h i r d phase of study dealt with casualty factors operating on a l l stages of the l i f e cycle of the weevil. In the adult stage r e l a t i v e abundance was assessed over a 3-year period by the use of a sp e c i a l l y designed trap and the mark-recapture p r i n c i p l e . By the use of th i s trap i n a variety of f i e l d plots the longevity of adults, the i r s u r v i v a l rate, egg laying behavior, d a i l y and seasonal a c t i v i t y patterns, host selection and the d i r e c t i o n and rate of dispersal on the forest f l o o r were investigated. The fecundity of adults was studied i n several f i e l d and laboratory experiments, - 207 -and by examinations of the female i n t e r n a l reproductive system. Other experiments were used to explore the influence of environmental conditions on a c t i v i t y . M o r t a l i t y factors of a l l stages were investigated, and assessed quantitatively i n the l a r v a l , pupal and young adult stages. Limited f i e l d and laboratory experiments were- conducted on the survival, percentage hatch and embryonic development of eggs. Attempts were made to assess the feeding behavior and early s u r v i v a l of young larvae upon i t s host, and of i t s adaptations for s u r v i v a l i n the r o o t - c o l l a r zone. Two aspects of concern were bark thickness and bark resin cavity characteristics. The structure and development of l a r v a l populations were analysed by head capsule width measurements. The period of pupal development and the characteristics of the pupal case structure were described. A fourth phase of study was concerned .with the effects of weevil injury to i t s host tree. Anatomical changes i n the host which resulted from direct l a r v a l feeding wounds were described. Growth losses r e s u l t i n g from p a r t i a l g i r d l i n g of pine root c o l l a r s were measured i n the v e r t i c a l and horizontal dimensions of the tree, using the three growth sequences described by Duff and Nolan (1953) . Some interpolations of these results were made of the forest as a whole to indicate economic effects, and to aid i n the understanding of weevil population development and surv i v a l . The b i o l o g i c a l factors considered most l i k e l y to influence weevil abundance and regulation of numbers are discussed i n r e l a t i o n to lodgepole pine stand development i n the Alberta f o o t h i l l s . Recommendations for control of the weevil through forest management are made for stands supporting high infestations. - 208 -CONCLUSIONS 1. In Alberta the geographical d i s t r i b u t i o n of H. warreni extends generally throughout the coniferous forest areas of pine and white spruce, except a l l stands above 5000 feet i n elevation. Lodgepole pine i s the primary host i n Alberta and within i t s range greatest abundance of the weevil occurs i n the Lower F o o t h i l l s Section (B19a of Rowe, 1959), between 2500 and 1+000 feet i n elevation. 2 . Within even-aged lodgepole pine stands weevils are most abundant on good growing sites characterized by a r i c h ground floral.complex of mosses, herbs and low shrubs, and where s o i l conditions are mesic to moist. Stands with a predominant moss carpet are generally associated with low levels of weevil abundance. :•. 3 . Decaying logs lying at tree bases are associated with heavy l a r v a l feeding damage i n the immediate areas of the roots and root c o l l a r of host trees. Their presence enhances moisture conditions i n the l a r v a l universe and provide a safe medium for mature larvae, pupae and tenerals. A r e l a t i v e l y high degree of forest f l o o r undulation and indentations, caused by tree uprooting and decaying logs, tend to favor high weevil populations as compared to stands having a smooth forest f l o o r . 1+. Within even-aged pine stands weevil numbers vary according to four main stand variables: stand density, tree size, stand maturity and duff depth. V a r i a b i l i t y i n the patterns of weevil abundance i s manifest i n the interactions between these variables. 5. Weevil numbers measured on an absolute scale attained a maximum - 209 -at a stand density range of 426 - 506 stems per acre i n a 65-70-year old stand. In stands 15-25-years old the density range for maximum numbers appeared to be far greater. 6. Within each stand type the numbers of weevils vary d i r e c t l y with tree size, being the highest on dominant trees and lowest on suppressed trees. Their numbers may be d i r e c t l y proportional to the surface area of the r o o t - c o l l a r region inhabited by larvae. The relationship i s applicable i n young and old stands. 7. The effect of stand maturity oh weevil numbers i s manifest i n the d i s t r i b u t i o n of tree sizes i n that attack density per tree i s lower i n young stands than i n older stands. On i n d i v i d u a l trees up to 25 years old the numbers of larvae r a r e l y exceed 3 while i n 65-70-year old trees the numbers often exceed 15 weevils. Absolute numbers of weevils, can occur at similar levels i n young and old stands, thus r e f l e c t i n g the influences of tree size and stand density. 8. The pattern of weevil abundance i n r e l a t i o n to duff depth i s complex, being influenced largely by duff depth at tree bases, duff quality and the effect of tree size. Within even-aged stands weevil numbers tend to increase d i r e c t l y with duff depth for each tree size class, but the slope of l i n e increases with tree size class. This seems due to the finding that a greater proportion of large trees have deeper duff than small trees of the same stand, and to the finding that the l a r v a l universe expands down the roots as the tree grows. 9. The d i s t r i b u t i o n of the weevil on i t s host tree varies i n time as the tree grows. The greatest percentage of weevils occur i n the root - 210 -c o l l a r zone and a lower percentage occur on roots. As tree size increases there i s a tendency for the percentage of weevils on roots to increase accordingly. Weevil numbers on the root c o l l a r and on roots each display a similar pattern of increase with increasing duff depth, but the pattern i s modified by tree size i n both cases. 10. The proportion of weevils on root and c o l l a r areas may change from year to year or during a summer period, i n response to changing moisture conditions around the tree base. 11. A clearcut form of tree harvest reduced a weevil population by an estimated 67 percent, but some larvae developed to adults i n the cut stumps one and two years after tree removal. The rate of development of surviving larvae and pupae appeared to be increased i n the cut stumps, probably due to higher s o i l temperatures at the base of cut stumps as compared to s o i l temperatures i n residual stands. A build-up of weevils occurs on border pine trees surrounding cut areas following clearcutting; t h e i r o r i g i n appears to be from adults dispersing from cut stumps, rather than from trees within residual stands. 12. I n i t i a l weevil invasion into young stands occurs when the trees are 6 -10 years old, or when they are "4-5 feet high and have a stump diameter of about 1 inch. During i n i t i a l invasion dominant trees are selected f i r s t and the rate of dispersal i s at least 35 - +5 feet per year. 13. Throughout the l i f e of the stand weevil attacks accumulate, being the highest on dominant trees and least on suppressed trees. The percentage of trees with current attacks i n mature stands relates d i r e c t l y to tree diameter, while the log of weevils per tree relates i n a linear - 211 -positive pattern with the percentage of trees having current attacks. The l a t t e r relationship forms the basis of a simple survey sampling technique for assessing weevil abundance and damage intensity. 14. Four general stages of weevil population development may be defined for even-aged lodgepole pine stands. The stages take into account • the period from i n i t i a l invasion u n t i l stand maturity. Stage I: extends from stand age 10-30 years; population development"characterized by slow rate of increase. Stage I I : extends from age 30-45 years; population development characterized by rapid rate of increase. Stage I I I : extends from age 45 to 70-&0 years; population development characterized by a general l e v e l l i n g - o f f . Stage IV: extends beyond age 70-80 years; population development characterized by a slow decline. The developmental patterns reflected i n these stages are more of an expression of population i n t e n s i t y than of absolute numbers. 15. Weevil populations are highly aggregated i n mature stands; "k" values of the negative binomial varied from O.09 to 0.68 while Taylor's power law provided an.aggregation index "b" value of I.92. 16. The tree c o l l a r zone of 'the l a r v a l habitat i s t r a n s i t i o n a l between l a t e r a l root bases and the lower portion of the main stem with respect to bark thickness and bark r e s i n cavity characteristics. Placement of eggs and young larvae i n t h i s zone may increase t h e i r s u r v i v a l . 17. The l i f e cycle of H. warreni extends about 2 years i n the Lower F o o t h i l l s Section of Alberta for complete development. In the l a r v a l stage only the f i r s t 3 instars are distinguishable by head capsule width measurement, but 5-7 instars are possible. Undetected high mortality or sampling errors may account for low numbers of early instar larvae i n f i e l d samples. The - .212 -period of pupal development i s r e l a t i v e l y constant from year to year. Pupae which do not develop to young adults "by f a l l do not appear to withstand overwintering conditions, whereas tenerals can. The proportion of the population undergoing pupation varies from year to year and with stand conditions, but most values l i e i n the range 5 -20 percent. Most young adults emerge from the pupal chamber before September. 18. The longevity of adults i s at least 3 years and eggs are l a i d during the second and t h i r d summers, the f i r s t summer of adulthood being an extended pre-oviposition period. Maximum egg productivity per female per season may be 36 but under natural f i e l d conditions the average may not exceed 12.2 eggs per female per season. The oviposition period extends from late May to September with a peak i n early July. Most eggs are deposited i n special niches excavated by the female i n the bark of the ro o t - c o l l a r zone, and subsequently covered over with excreta. Other eggs are deposited loosely under bark scales or i n the adjacent s o i l . Under f i e l d conditions the average period of embryonic development i s about k2 days. 19. F i r s t instar larvae can survive 5 or more days i n the f i e l d without food. During i n i t i a l bark penetration they require some form of support for leverage when chewing. A l l instars respond negatively i n the presence of l i g h t and each larva possesses 2 anterior o c e l l i . The depth of l a r v a l feeding i n the bark relates d i r e c t l y to l a r v a l size up to the fourth instar. Feeding damage i s confined to the phloem u n t i l the fourth instar and thereafter i t extends through cambial tissues as we l l . The average t o t a l length of gallery scored through cambium by mature larvae may not exceed 2h cm. The feeding gallery tends to be more circumferentially oriented - 213 -around the c o l l a r zone of small trees as compared to large trees, but as the tree grows the tendency i s toward irregularly-shaped patches of dead cambium on the r o o t - c o l l a r surface. This change of pattern l i k e l y r e f l e c t s the influences of accumulated damage as w e l l as weevil attack density. 20. An important mortality factor of larvae, prepupae, pupae and tenerals i s excess moisture i n the gallery and .pupal chamber. The incidence of parasites and predators on pre-pupae and pupae does not appear to account for more than 5 percent mortality of these stages. In the adult stage the incidence of mortality and factors affecting fecundity were p a r t l y i d e n t i f i e d . On the whole, the observed mortality of weevil' populations, exclusive of eggs and adults, was generally less than 5 percent. In some forest habitat situations eggs and early instar larvae may be the most c r u c i a l , while i n other habitat situations the pre-pupal and pupal stages may be most vulnerable to mortality. Successful oviposition appeared to be highly variable, being strongly dependent upon microhabitat conditions. 2 1 . Newly emerged males and females occur i n about equal numbers. Differences i n t h e i r behavior account p a r t l y for varying sex r a t i o s i n collections made i n d i f f e r e n t locations within stands as w e l l as during di f f e r e n t summer periods. Males tend to be more abundant at stand peripheries while females tend to be more numerous, within the stand. 2 2 . Adults are most active at t e r r e s t r i a l dispersion, mating, feeding and oviposition during June and early July, after which time there i s a general decline i n these a c t i v i t i e s . The decreasing trend coincides with generally hot and dry conditions i n July and August. 2 3 . Examinations of the internal reproductive structures of female - 214 -weevils can provide a r e l i a b l e index of sexual a c t i v i t y and of the general fecund condition. 24. The d a i l y and hourly a c t i v i t y patterns of adults suggest a dependence upon temperature, l i g h t and probably moisture conditions i n the forest. Throughout day l i g h t hours the adults remain i n the forest duff and emerge about 2 hours after sunset. Almost no emergence occurs i f temperatures at the forest f l o o r f a l l to 36-40 °F. by 11:00 p.m. At night adults climb trees to feed, or they disperse l a t e r a l l y i n search of new hosts. When leaving a tree of o r i g i n t h e i r i n i t i a l d i r e c t i o n of dispersal i s random, while the i r rate of dispersal from a fixed point tends to be maximal during any one day, but declines rapidly to a constant after 8-10 days. The rate of linear t r a v e l during any one night may relate to the mean distance between- trees.. Host trees are located at least p a r t l y by v i s i o n and the pattern of selection appears i d e n t i c a l for both sexes. 25. On young trees adult feeding occurs most heavily on lower branch bases and on upper branches of top whorls. On large trees feeding also occurs i n the main canopy. 26. The studies provide insight into some weevil-host interactions. Different patterns of oviposition and l a r v a l d i s t r i b u t i o n s occur between small and large hosts. These differences account for some of-the higher incidence of mortality recorded i n regeneration pine. Various degrees of p a r t i a l g i r d l i n g , accumulated throughout stand development, may account for height and diameter growth losses, but .the o v e r a l l effect of weevil damage does not influence s i g n i f i c a n t changes i n stand density 05P stand structure. The v e r t i c a l sequence of stem analysis appeared to be the most useful of the - 215 -three sequences i n expressing the effects of weevil damage on pine. In the temporal sense natural successional changes may be hastened through the effects of the weevil, especially i n stands where populations remain high over long periods of time. Anatomical changes i n the r o o t - c o l l a r zone arise as a re s u l t of l a r v a l feeding, and they provide some resistance against the d i r e c t and i n d i r e c t effects of wounding. At the s i t e of wounds a continuous r e s i n flow i s imperative to the safety of developing larvae. Pre-pupae, pupae and tenerals also derive protection from a resin-bark fragment matrix. 2 7 . The investigations have provided several techniques to measure and evaluate weevil abundance i n a variety of pine stand conditions. These include a simple sampling system for general surveys, a sampling system for intensive population studies and a method of live-trapping adults for f i e l d behavior studies and numerical assessment using the mark-recapture p r i n c i p l e . 2 8 . The studies have revealed insight into the possible mechanisms by which weevil abundance i s regulated i n lodgepole pine forests, i n both the short and long term sense. 29. The studies provide a b i o l o g i c a l basis for prescribing several control measures against the weevil through forest management. . - 216 -LITERATURE CITED 1. Angus, T. A. i960. Microbiological control of forest insects - a new approach. Canad. Pulp Pap. Industr. 1 3(ll) : 65-66, 68, 70-71. 2 . Annual Report of the Forest Insect and Disease Survey, For. B i o l . Div., Can. Dept. A g r i c , 1956 : 72-76. 3. Baranyay, J. A. and G. R. Stevenson. I96I+. Mortality caused by A r m i l l a r i a root rot, Peridermium rusts, and other destructive agents i n lodgepole pine regeneration. For. Chron. 1+0(3) : 350-361. 1+. Benham, R. W. and J. L. Miranda. 1953- The genus Beauveria, morphological and taxonomic studies of several species and of two strains isolated from wharf-piling borers. Mycologia 1+5 : 727-7I+6. 5. 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