UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Blackflies (Diptera: Simuliidae) : a problem review and evaluation Watts, Susan B. 1975

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1975_A6 W38_7.pdf [ 5.79MB ]
Metadata
JSON: 831-1.0075115.json
JSON-LD: 831-1.0075115-ld.json
RDF/XML (Pretty): 831-1.0075115-rdf.xml
RDF/JSON: 831-1.0075115-rdf.json
Turtle: 831-1.0075115-turtle.txt
N-Triples: 831-1.0075115-rdf-ntriples.txt
Original Record: 831-1.0075115-source.json
Full Text
831-1.0075115-fulltext.txt
Citation
831-1.0075115.ris

Full Text

BLACKFLIES A PROBLEM (DIPTERA: SIMULIIDAE): REVIEW AND EVALUATION by SUSAN B. WATTS B . S c , U n i v e r s i t y C o l l e g e o f North Wales, Bangor, A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY i n the F a c u l t y o f FORESTRY We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF J u l y , BRITISH COLUMBIA 1975 In presenting t h i s t h e s i s in p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that 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 or reference and study. I f u r t h e r agree that permission for extensive copying 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 granted by the Head of my Department or by h i s re p r e s e n t a t i v e s . It i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date T T u X ^ j jSPtr. ABSTRACT An e x t e n s i v e review h e r e i n of world l i t e r a t u r e on b l a c k f l i e s ( D i p t e r a : Simuliidae L a t r e i l l e ) with r e f e r e n c e s extending over n e a r l y two c e n t u r i e s , and addressed to d i v e r s e i n t e r e s t groups, has h i g h l i g h t e d the importance of these f l i e s , t h e i r b i o l o g i c a l and resource-use impacts, the advances i n knowledge concerning them, the gaps i n the i n f o r m a t i o n , the o b s t a c l e s to p r o g r e s s , the hazards of a p p l y i n g i l l - c o n s i d e r e d h e r o i c measures to cope w i t h them, and the d i r e c t i o n s which r e s e a r c h might p r o f i t a b l y pursue. Needs remain f o r c l e a r e r understanding of the components of b l a c k f l y behaviour i n g e n e r a l , and at a s p e c i e s l e v e l , w i t h due r e g a r d to determinant f a c t o r s i n a t t r a c t a n c e and r e p e l l e n c e as these decide proneness to a t t a c k . Needs remain f o r a c l e a r e r u n d e r s t a n d i n g of the f a c t o r s of d i f f e r e n t i a l and changing p h y s i o l o g i c a l r e a c t i o n of the host to the t o x i n i n j e c t e d by the f l i e s . Other needs remain f o r more thorough documentation of resource impacts caused by these i n s e c t s . A great need remains f o r more complete understanding of the p o p u l a t i o n ecology o f b l a c k f l i e s , as w e l l as t h e i r r o l e among primary consumers, and as food organisms themselves, i n food chains i n b e n t h i c ecosystems. i v CONTENTS " Page ABSTRACT . i i i TABLE OF CONTENTS '.. i v FIGURES ............ v i i ACKNOWLEDGEMENTS . . ... . v i i i INTRODUCTION 1 1. THE INDIVIDUAL ORGANISM 6 1.1 MORPHOLOGY 6. 1.1.1 A d u l t morphology 7 1.1.2 L a r v a l and pupal morphology 10 1.1.3 Egg morphology 14 1.2 REPRODUCTION, GROWTH AND MORPHOGENESIS 14 1.2.1 Rep r o d u c t i o n 14 1.2.2 Morphogenesis and growth 16 1.3 FEEDING ......... ... 17 1.3.1 L a r v a l f e e d i n g 18 1.3.2 A d u l t f e e d i n g 18 - Feeding mechanism 19 1.4 FLIGHT 21 1.5 BEHAVIOUR 23 1.5.1 V i s u a l host' f a c t o r s of importance i n a t t r a c t i o n 25 - Colour , . 2 5 - Shape, movement and contour 28 1.5.2 A i r b o r n e host f a c t o r s of importance i n a t t r a c t i o n . 31 - Temperature and moisture 31 - Sweat 34 - C a r b o n d i o x i d e •••• ^ 2. THE SPECIES CONCEPT 42 2.1 GEOGRAPHICAL DISTRIBUTION 42 2 . 2 TAXONOMY 43 V Page 3. THE ROLE OF BLACKFLIES IN ECOSYSTEMS 47 3.1 PREDATOR, PARASITE AND COMPETITOR RELATIONSHIPS ... 47 3.1.1 Predators 47 3.1.2 P a r a s i t e s 50 - M i c r o s p o r i d i a 50 - Mermithids 51 - Fungi 52 3.1.3 Competitors 52 3.2 THE ROLE AND IMPORTANCE OF BLACKFLY LARVAE AND ADULTS IN FOOD CHAINS 53 3.2.1 F i s h food chains 55 3.2.2 Avia n food chains 58 4. THE IMPACT OF BLACKFLIES ON THEIR HOSTS 60 4.1 THE SPECIES INVOLVED 60 4.2 HOST REACTIONS 60 4.2.1 C l i n i c a l d e t a i l s o f host r e a c t i o n s 62 4.3 DISEASE TRANSMISSION .. 64 4.3.1 Human o n c h o c e r c i a s i s 65 4.3.2 Bovine o n c h o c e r c i a s i s 67 4.3.3 L e u c o c y t o z o o n i a s i s of b i r d s 68 4.3.4 Other d i s e a s e s 69 5. THE IMPACT OF BLACKFLIES ON NATURAL RESOURCE USE AND DEVELOPMENT 71 5.1 THE EFFECTS OF BLACKFLIES ON LABOUR FORCE EFFICIENCY AND GROUP MORALE 72 5.2 THE IMPACT OF BLACKFLIES ON RECREATIONAL ACTIVITIES 74 5.3 THE IMPACT OF BLACKFLIES ON FOREST RANGE MANAGEMENT 7 5 6. PRINCIPLES, PRACTICES AND PROBLEMS IN CONTROL OF BLACKFLIES 79 6.1 DEPOPULATION 80 6.1.1 C h e m i c a l l y induced d e p o p u l a t i o n 81 6.1.2 B i o l o g i c a l c o n t r o l 87 6.1.3 H a b i t a t management 88 6.2 PERSONAL PROTECTION 89 SUMMARY 92 v i Page CONCLUSIONS • 93 APPENDIX 96 GLOSSARY 99 LITERATURE CITED 100 v i i LIST OF FIGURES Page FIGURE 1. A d u l t b l a c k f l y Prosimulium mixtum (X15) 8 2. The mature l a r v a of a b l a c k f l y , Odagmia ornata, l a b e l l e d to show the v a r i o u s p a r t s . (X18) l x 3. The heads of ( a) a female, (b) a male of a s p e c i e s o f Simulium, showing the mouth p a r t s 20 4. A s i m p l i f i e d f a m i l y t r e e o f the order D i p t e r a . 44 5. T r o p h i c l e v e l s i n food chains i n v o l v i n g b l a c k f l i e s . 54 v i i i ACKNOWLEDGEMENTS The author wishes to express her deepest g r a t i t u d e to Dr. K. Graham, t h e s i s s u p e r v i s o r , f o r h i s constant guidance, a d v i c e , and encouragement throughout the p r e p a r a t i o n of t h i s t h e s i s . The author a l s o extends thanks to Drs. D.A. C r a i g , U n i v e r s i t y of A l b e r t a , and R.W. Crosskey, B r i t i s h Museum, London, f o r t h e i r h e l p f u l comments and a d v i c e . The r e s e a r c h was made p o s s i b l e through funding p r o v i d e d by the N a t i o n a l Research C o u n c i l o f Canada, grant #67-0743, and The U n i v e r s i t y of B r i t i s h Columbia. M O T \ A v o R O F ( L K £ j _ , \ S i O T T f t V J f\ • XX THE BLACKFLY SONG by Wade Hemsworth Twas e a r l y i n the s p r i n g when I decide to go For to work up i n the woods i n North O n t a r - i - o , And the unemployment o f f i c e s a i d they'd send me t h r u To the L i t t l e A b i t i b i w i t h the survey crew. CHORUS: And the blackflies - the little blackflies3 Always the blackfly no matter where you gos 11ll die with my blackfly a-pickin ' my bones In north Ontar-i-o -i-o In north Ontar-i-o -i-o The man Black Tobey was the c a p t a i n of the crew And he s a i d I'm gonna t e l l you boys, what we're gonna do. They want to b u i l d a power dam and we must f i n d a way For to make the L i t t l e Ab flow around the o t h e r way. (Chorus) So we survey to the east and we survey to the west And we c o u l d n ' t make our minds up how to do i t b e s t . L i t t l e Ab, L i t t l e Ab what s h a l l I do For I'm a l l but g o i n ' c r a z y w i t h the survey crew. (Chorus) Twas b l a c k f l y , b l a c k f l y everywhere A - c r a w l i n ' i n your whiskers, a - c r a w l i n ' i n your h a i r , A-swimmin' i n the soup and a-swimmin' i n the t e a , Oh the d e v i l take the b l a c k f l y and l e t me be. (Chorus) Black Tobey f e l l to swearin' cause the work went slow, And the s t a t e of our morals was g e t t i n ' p r e t t y low, And the f l i e s swarmed heavy -i t was hard to c a t c h a b r e a t h As you staggered up and down the t r a i l a - t a l k i n ' to y o u r s e l f . (Chorus) Now the b u l l cook's name was B l i n d R i v e r Joe; I f i t hadn't been f o r him we'd've never p u l l e d through For he bound up our b r u i s e s and he kidded us f o r fun, And he l a t h e r e d us w i t h bacon , grease and balsam gum. (Chorus) At l a s t the job was over; Black Tobey s a i d - We're through w i t h the L i t t l e A b i t i b i and the survey crew. Twas a wonderful experience and t h i s I know I ' l l never go a g a i n to North O n t a r - i - o . (Chorus) - 1 -INTRODUCTION There might h a r d l y e x i s t any f a m i l y of organisms which encompasses a g r e a t e r spectrum of b i o l o g i c a l , e nvironmental, e c o l o g i c a l , m e d i c a l , economic, and s o c i o l o g i c a l i n t e r e s t s and problems on a world-wide s c a l e than the b l o o d - s u c k i n g f l i e s o f the Dipterous f a m i l y Simuliidae. These f l i e s are known i n the E n g l i s h language as b l a c k f l i e s , b u f f a l o gnats, s a n d f l i e s , or turkey gnats, and i n the l i t e r a t u r e of other languages they are found under such names as Kriebelmucken (German), Moscas de c a f e (Mexican), Mouches de coloumbatz (Roumanian), and Mouches n o i r e s (French). They are not to be confused w i t h -a group of phytophagous aphids which a l s o are known as b l a c k f l i e s . Those who are f a m i l i a r w i t h these i n s e c t s r e c o g n i s e them as small b l a c k or reddish-brown humped-back f l i e s , whose g e n e r a l form i s r e m i n i s c e n t of the North American " b u f f a l o " or b i s o n . From t h i s s i m i l a r i t y they have been awarded the s c i e n t i f i c name "Simulium" from the L a t i n word simulare, to s i m u l a t e . B l a c k f l i e s are s i g n i f i c a n t p r i m a r i l y f o r the c o m p l i c a t i o n s a s s o c i a t e d w i t h the b l o o d - s u c k i n g a c t i v i t i e s o f the a d u l t females on humans, and on v a r i o u s w i l d and domestic b i r d s and mammals. A few s p e c i e s are e n t i r e l y a n t h o p h i l i c , n e c t a r - s e e k i n g , and thus e n t i r e l y innocuous, but the n e c t a r - s e e k i n g h a b i t i s shared a l s o by haematophagous s p e c i e s . In t h e i r p u r s u i t of b l o o d , b l a c k f l i e s harass t h e i r h o s t s , d i s r u p t the g r a z i n g a c t i v i t i e s of ungulates and t h e i r herd o r g a n i z a t i o n , h i n d e r s u c k l i n g by c a l v e s , and d e l a y the r e p r o d u c t i v e process i n c a t t l e . The consequent l a t e b i r t h s may render the young animals p o o r l y prepared f o r the r i g o r s o f - 2 -- • w i n t e r . The b l o o d - f e e d i n g causes blood d e f i c i e n c i e s and bl o o d -c e l l a b n o r m a l i t i e s i n humans. V a r i o u s dermal, pulmonary and systemic r e a c t i o n s r e s u l t from envenomization by s a l i v a r y t o x i n s of the f l i e s . In severe cases death accrues from a n a p h y l a c t i c shock. The importance of these i n s e c t s as a cause of human d i s -comfort i s t e s t i f i e d by t h e i r being f e a t u r e d i n a po p u l a r song "The b l a c k f l y song" (see p r e f a c e ) . B l a c k f l i e s are s i g n i f i c a n t a l s o f o r t h e i r t r a n s m i s s i o n o f v i r u s e s , p r o t o z o a , and m i c r o f i l a r i a l nematodes to human, mammalian and av i a n h o s t s . These agents v a r i o u s l y cause i l l n e s s , b l i n d n e s s , dermal l e s i o n s and death. In t h e i r i n j u r i o u s a c t i v i t e s b l a c k f l i e s p r e s e n t problems of worldwide occurrence and importance f o r t h e i r e f f e c t on human h e a l t h , r e c r u i t m e n t and e f f i c i e n c y of the f o r e s t i n d u s t r i e s labour f o r c e , r e c r e a t i o n a l use of f o r e s t a r e a s , e f f e c t i v e n e s s o f range-management f o r c a t t l e , game, waterfowl and domestic fowl p r o d u c t i o n . In some re g i o n s o f the world where b l a c k f l i e s t r a n s m i t d i s e a s e to humans, v a l u a b l e a g r i c u l t u r a l l a n d along r i v e r v a l l e y s has been abandoned because of the a f f l i c t i o n s conveyed to people by these i n s e c t s . The a d u l t s i n f l i g h t are f e d upon by v a r i o u s predaceous i n s e c t s such as d r a g o n f l i e s , c e r t a i n s p e c i e s of predaceous D i p t e r a , and by b i r d s , n o t a b l y swallows. Hence they c o n s t i t u t e an important item i n the food c h a i n of other organisms. In the l a r v a l stage b l a c k f l i e s a re an important form o f a q u a t i c l i f e a t t a c h e d to stones and v e g e t a t i o n i n r i v e r s and f a s t - 3 -f l o w i n g streams, as w e l l as to the s p i l l w a y s o f dams. In these h a b i t a t s they feed upon micro-organisms and are i n t u r n f e d upon by a q u a t i c l a r v a e of other i n s e c t groups, and a l s o c o n s t i t u t e an important item i n the food r e s o u r c e s of f i s h i n streams. It. i s e v i d e n t t h a t c o n t r o l of b l a c k f l y p o p u l a t i o n s cannot be undertaken without due r e g a r d to other consequences. A s p e c i a l i n t e r e s t i n b l a c k f l i e s d e r i v e s from the s u i t a b i l i t y of t h e i r chromosomes f o r the study of g e n e t i c s . The concern over and i n t e r e s t i n b l a c k f l i e s has generated a great amount of r e s e a r c h on many aspects of the s u b j e c t . S t u d i e s deal w i t h the v a r i o u s b i o m e d i c a l problems a s s o c i a t e d with these f l i e s . A few s t u d i e s r e c o r d r a t h e r s k e t c h i l y the impact o f the f l i e s on r e s o u r c e use and development. I n v e s t i g a -t i o n s aimed at a l l e v i a t i n g the problem have sought to do so by p o p u l a t i o n r e d u c t i o n through a q u a t i c h a b i t a t c o n t r o l , chemical treatment of streams and r i v e r s , and by evading a t t a c k s by p r o v i s i o n of s h e l t e r s , a p p l i c a t i o n o f r e p e l l e n t s and d e t e r r e n t s , and t h e r a p e u t i c treatment of b i t e s and i n f e c t i o n s . The l i t e r a t u r e i s w i d e l y s c a t t e r e d i n s c i e n t i f i c p u b l i c a -t i o n s i n v a r i o u s languages, addressed to such d i f f e r e n t audiences as e n t o m o l o g i s t s , p h y s i c i a n s , p a r a s i t o l o g i s t s , and f i s h e r i e s b i o l o g i s t s , t h a t no coherent and comprehensive account i s a v a i l a b l e as a b a s i s f o r e v a l u a t i n g the p r e s e n t s t a t e of knowledge, the gaps i n knowledge, or the d i r e c t i o n s needed f o r r e s e a r c h . S e r i o u s problems e x i s t through the c o n f u s i o n i n taxonomy, such that proper f i l i n g and r e t r i e v a l of meaningful i n f o r m a t i o n i s s e r i o u s l y h i n d e r e d . Other problems r e s i d e i n - 4 -the l a c k of c a r e f u l documentation of resource impacts caused by these i n s e c t s . Many of the e a r l i e r works are of r e f i n e d c a l i b e r , but many are now inadequate i n the l i g h t of p r e s e n t knowledge. With some no t a b l e e x c e p t i o n s , progress has been hampered by a f a t a l i s t i c a t t i t u d e toward the acceptance of misery, f o l l o w i n g the assump-t i o n t h a t l i t t l e can be done about i t . Along w i t h t h i s a t t i t u d e i s the f a c t t h a t f i r m documentation i s l a c k i n g on the q u e s t i o n of v a r i o u s impacts o f these i n s e c t s . Thus a v i c i o u s c i r c l e i s set-i n t o motion: why s o l v e a problem whose dimensions are unknown, and why measure the dimensions when there i s no c l e a r promise o f a s o l u t i o n to the problem' The p r e s e n t p a u c i t y of i n f o r m a t i o n and of understanding, not o n l y impedes p r o g r e s s ; i t a l s o c a r r i e s the grave r i s k t h a t , w i t h i n c r e a s i n g p r e s s u r e s on the development of the h i n t e r l a n d s , e n v i r o n m e n t a l l y i n j u r i o u s a c t i o n s may be made at any time by groups who decide to apply h e r o i c t a c t i c s w i t h i l l - c o n c e i v e d measures which l a c k an o v e r a l l s t r a t e g i c p e r s p e c t i v e . I t i s e v i d e n t that a need e x i s t s f o r c l e a r e r assessment o f b l a c k f l i e s as a problem i n human w e l f a r e , work e f f i c i e n c y , and resource uses. A need e x i s t s a l s o f o r c o l l a t i o n and evalua-t i o n o f the s p e c i f i c problems and o f the l i t e r a t u r e c o n c e r n i n g the s p e c i f i c f a c t s , a l l e g e d f a c t s , and s p e c u l a t i o n s p e r t a i n i n g to the b i o l o g y and ecology of these i n s e c t s . Thereby t h e i r p o s s i b l e inadequacies may be p i n p o i n t e d and d e l i n e a t e d f o r p r o d u c t i v e r e s e a r c h o b j e c t i v e s . Without such c r i t i c a l e v a l u a t i o n being made, the major needs may remain obscure, the more pro-d u c t i v e l i n e s may remain n e g l e c t e d or s u b j e c t to the c a p r i c e of - 5 -human whims, and combative methods w i l l remain e m p i r i c a l , i n f e r i o r , and p o s s i b l y e n v i r o n m e n t a l l y d e t r i m e n t a l . A c c o r d i n g l y the purpose and scope of t h i s t h e s i s are set w i t h i n the broad framework of b l a c k f l i e s as a group of worldwide occurrence and importance. The d i v e r s e b i o l o g i c a l , e c o l o g i c a l , resource impact and combative phenomena are assessed. D i r e c t i o n s f o r s i g n i f i c a n t r e s e a r c h are h i g h l i g h t e d . - 6 -1. THE INDIVIDUAL ORGANISM 1.1 MORPHOLOGY I t seems worthwhile to place the subject of morphology of b l a c k f l i e s i n the p e r s p e c t i v e of i t s purpose, f o r h e r e i n r e s i d e some of the problems of understanding them and of seeking means of coping w i t h them. A knowledge of general s t r u c t u r e of a l l metamorphic stages of the group as a whole, and p a r t i c u l a r s of the d i f f e r e n t species w i t h i n the group, merits a t t e n t i o n f o r the purpose of e s t a b l i s h i n g a f i r m foundation f o r a l l other work. I t provides a d e f i n i t i o n of the b a s i c plan to which a l l members of the group can be r e l a t e d , assigned a f a m i l y group i d e n t i f y , and d i f f e r e n t i a t e d from other groups. Within the group, a d e s c r i p t i o n of the d i f f e r e n t morphs as the i n s e c t evolves o n t o g e n e t i c a l l y forms an e s s e n t i a l p a r t of a d e f i n i t i o n of a group i d e n t i t y . V a r i a t i o n s on d e t a i l s w i t h i n the b a s i c plan provide the b a s i s f o r d i s t i n g u i s h i n g s u c c e s s i v e l y lower taxonomic ranks to genus and species. D e t a i l s of the e x t e r n a l anatomy provide a map f o r the e x p l o r a t i o n of f u n c t i o n a l d e t a i l s such as the k i n d and d i s t r i b u t i o n of sense organs, which may then be i n t e r p r e t e d and explored experimentally. D e t a i l s of the i n t e r n a l anatomy are important i n respect to the i n v e s t i g a -t i o n of s a l i v a r y glands, t h e i r chromosomes, s e c r e t i o n s , and p o s s i -ble immunological research. Other i n t e r n a l s t r u c t u r e s may be r e l e v a n t to the study of food requirements. Such st u d i e s may i n -volve examination of the alimentary t r a c t of a d u l t s and/or l a r v a e , or examination of t h e c o n d i t i o n of o v a r i e s , t e s t e s , or s t a t e of - 7 -i n s e m i n a t i o n , as any of these may a f f e c t the b l o o d - s u c k i n g h a b i t . The r e l a t i v e c o n s i s t e n c y of m o r p h o l o g i c a l d e t a i l s of a d u l t s and l a r v a e of such a u b i q u i t o u s group as the s i m u l i i d s i s remarkable. I t i s a cause of d i f f i c u l t i e s and disagreements among taxonomists who have d i f f e r e n t concepts f o r d i v i d i n g the f a m i l y i n t o genera, and genera i n t o s p e c i e s . With such d i f f i c u l -t i e s i n taxonomy, we f i n d t h a t other i n f o r m a t i o n which depends on c o r r e c t and c o n s i s t e n t i d e n t i f i c a t i o n , i s c o n f u s i n g . From an e v o l u t i o n a r y p o i n t of view, one might i n f e r t h a t the f l u v i a l environment has imposed l i m i t a t i o n s on the scope f o r d e v i a t i o n s from the common p l a n . It i s c o n c e i v a b l e , f o r example, t h a t . b l a c k f l y l a r v a e have evolved an a d a p t a t i o n to a n i c h e g e n e r a l l y c h a r a c t e r i s e d by c o l d f a s t - f l o w i n g water, where attachment to s u b s t r a t a i s w i t h i n t h e i r means, a p p r o p r i a t e s u p p l i e s of food and oxygen are o b t a i n a b l e , where low water temperatures and f a s t - f l o w i n g water may reduce c o m p e t i t i o n and p r e d a t i o n . I t i s a l s o c o n c e i v a b l e that m o r p h o l o g i c a l a d a p t a t i o n s which enable the a d u l t s to emerge from a f l o w i n g a q u a t i c medium, and to d i v e i n t o i t f o r egg d e p o s i t i o n , have imposed other l i m i t a t i o n s on m o r p h o l o g i c a l d i v e r s i t y . 1.1.1 A d u l t morphology B l a c k f l i e s c o n s t i t u t e the f a m i l y Simuliidae ( D i p t e r a : Nematocera). They are a very homogenous group and can be e a s i l y r e c o g n i s e d i n both a d u l t and l a r v a l stages by t h e i r g e n e r a l form, as w e l l as by c e r t a i n unmistakable taxonomic c h a r a c t e r i s t i c s . The d i f f e r e n t s p e c i e s are so s i m i l a r i n g e n e r a l appearance, and the d i s t i n g u i s h i n g c h a r a c t e r i s t i c s are so d i f f i c u l t to a s c e r t a i n , - 8 -FIGURE 1. ADULT BLACKFLY, PROSIMULIUM MIXTUM (XI5) FROM: Peterson, B.V. (1970). - 9 -that many s p e c i e s ' d e s c r i p t i o n s i n the l i t e r a t u r e might e q u a l l y w e l l serve f o r s e v e r a l s p e c i e s . T h i s has l e d to obvious problems and c o n f u s i o n i n taxonomy. A d u l t f l i e s are s m a l l , ranging i n s i z e from 1-6 mm., and most s p e c i e s are d i s t i n c t l y black-pigmented, though many appear s i l v e r y or y e l l o w from t h e i r dense v e s t i t u r e of s h o r t g l i s t e n i n g h a i r s . Other s p e c i e s are brown, y e l l o w or orange-pigmented. The thorax of the a d u l t f l y p r e s e n t s a str o n g development of the scutum and r e d u c t i o n of the prescutum, r e s u l t i n g i n a prominent hump, which, to g e t h e r w i t h the low-held head, has l e d these f l i e s to be c a l l e d " b u f f a l o gnats" i n the p a s t . Some s p e c i e s o f b l a c k f l y are able to d i s p e r s e great d i s t a n c e s , and a c c o r d i n g to Lewis (1957), some can crawl underwater, i n d i c a -t i n g obvious s t r e n g t h o f body c o n s t r u c t i o n . The one p a i r o f wings i s broad and sh o r t w i t h d i s t i n c t l y t h i c k e n e d l o n g i t u d i n a l v e i n s crowded toward the l e a d i n g edge, other v e i n s are i n d i s t i n c t . U n l i k e otherNematocera, the antennae of b l a c k f l i e s are short and s t o u t , u s u a l l y no longer than the head i t s e l f . In both sexes the antennae are devoid o f the long sensory whorls o f h a i r c h a r a c t e r i s t i c o f mosquitoes (Culiaidae) and b i t i n g midges (Ceratopogonidae). In the female b l a c k f l y the eyes are d i c h o p t i c , i . e . w i d e l y separated by the f r o n s , while i n the male the eyes are h o l o p t i c ( c o n t i g u o u s ) , and the upper f a c e t s can be s h a r p l y d i f f e r e n t i a t e d from the lower ones. T h i s d i f f e r e n c e i n eye s i z e between the sexes i s an easy way of approximately s o r t i n g the sexes. O c e l l i are absent. - 10 -Mouth p a r t s d i f f e r q u i t e markedly between the sexes as i t i s o n l y the female t h a t i s ever adapted to take a b l o o d meal. It should a l s o be noted t h a t i n some s p e c i e s of b l a c k f l i e s the females are n o n - b i t i n g , and have m a x i l l a e and mandibles without s e r r a t e d edges. G e n e r a l l y , the b l o o d - f e e d i n g female possesses a s h o r t , s t o u t b l a d e - l i k e labrum having a f i n e l y s e r r a t e d t i p r e m i n i s c e n t of the toothed t i p of a g r a p e f r u i t k n i f e . I t i s so formed t h a t i t i n c i s e s the s k i n , cuts through c a p i l l a r i e s , and wedges the wound open w h i l e the mandibles and m a x i l l a e , a l s o s e r r a t e d , s i n k i n t o the wound. The mandibles and m a x i l l a e are c h a n n e l l e d i n such a way that when working together they p r o v i d e s a l i v a r y and food c a n a l s . The mandibles resemble broad f l a t p l a t e s , w i t h the l e f t blade over the r i g h t a l l o w i n g t r a n s v e r s e c u t t i n g movements to a i d p e n e t r a t i o n . The m a x i l l a r y blades are the galeae, which are housed, together w i t h the mandibles and the hypopharynx, i n the wide s o f t labium. Male b l a c k f l i e s are presumed to feed on n e c t a r and no r e c o r d e x i s t s of them sucking b l o o d . T h e i r mouth p a r t s are s i m i l a r to the females but are c o n s i d e r a b l y weaker, l a c k i n g the s t r e n g t h to p e n e t r a t e s k i n , a l s o the m a x i l l a e and mandibles l a c k c u t t i n g t e e t h . The a c t u a l f u n c t i o n of each mouth p a r t component, and the sequence of movements i n v o l v e d i n p e n e t r a t i o n of the s k i n , l a c k s f u l l d e s c r i p t i o n i n the l i t e r a t u r e . 1.1.2 L a r v a l and pupal morphology B l a c k f l y l a r v a e have many d i s t i n g u i s h i n g f a m i l y c h a r a c t e r -i s t i c s , and can be f a i r l y e a s i l y r e c o g n i s e d i n the f i e l d . A l l - 11 FIGURE 2. THE MATURE LARVA OF A BLACKFLY ODAGMIA ORNATA, LABELLED TO SHOW THE VARIOUS PARTS (XI8) mouth b r u . t v ^ ^ mandible «ntennav /gS? ^ m _ , M U /hypo pharynx spot-respiratory filament salivary aland p o s t e r i o r s u c k e r FROM: C a r l s s o n , G. (1962). - 12 members of the f a m i l y are a q u a t i c , i n h a b i t i n g f a s t - f l o w i n g streams and r i v e r s throughout the world. Although c e r t a i n d i a g n o s t i c f e a t u r e s w i l l i d e n t i f y a b l a c k f l y l a r v a p e r s e , i t i s e s p e c i a l l y important, f o r c o r r e c t f i l i n g and r e t r i e v a l of i n f o r m a t i o n , to be able to r e c o g n i s e i n d i v i d u a l s p e c i e s when i n i t i a t i n g a c o n t r o l program, or, f o r t h a t matter, when under-t a k i n g any b i o l o g i c a l s t u d i e s . U n l i k e other Nematocera, which i n v a r i a b l y have f o u r l a r v a l i n s t a r s , b l a c k f l i e s are s t a t e d to have s i x , seven, e i g h t or nine such i n s t a r s , depending on the source of r e f e r e n c e and upon the s p e c i e s under d i s c u s s i o n . Mature l a r v a e range i n l e n g t h from 4.5-12 mm. (Crosskey. 1973), and are c h a r a c t e r i s t i c a l l y r a t h e r swollen i n the t h o r a c i c r e g i o n and p o s t e r i o r l y i n the abdomen. I n d i v i d u a l s v a r y q u i t e c o n s i d e r a b l y i n c o l o u r from grey to b l a c k , blackish-brown and o f f - w h i t e . Although the t y p i c a l b l a c k f l y l a r v a i s r e c o g n i s e d as b e a r i n g a p a i r , o f l a r g e c e p h a l i c fans on the head, a t y p i c a l s p e c i e s do occur i n which the fans appear reduced (Cvozetia ovoz'etense and Simulium ovioeps) and, furthermore, f a n l e s s s p e c i e s do o ccur, i . e . Gymnopais and Twinnia ( C r a i g 1974). Very l i t t l e l i t e r a t u r e i s a v a i l a b l e on these a t y p i c a l s p e c i e s , and most d e s c r i p t i v e documents on b l a c k f l i e s ignore them a l t o g e t h e r . The c e p h a l i c fans are n o r m a l l y h e l d extended by i n t e r n a l f l u i d p r e s s u r e so as to a c t as food f i l t r a t i o n organs i n the c u r r e n t of the stream or r i v e r (Wood et al.1962). In t h e i r f i n e s t r u c t u r e these c e p h a l i c fans may be of taxonomic v a l u e . - 13 -Antennae o f the l a r v a e can act as d i a g n o s t i c f e a t u r e s . Although a l l s p e c i e s appear to have four-segmented antennae, the r a t i o s of the lengths of v a r i o u s segments and a n n u l i to one another, and the number of a n n u l i are of d i a g n o s t i c value to s p e c i e s i d e n t i f i c a t i o n where such d e t a i l s are r e c orded. Mouth p a r t s c o n s i s t of h a i r e d m a x i l l a e , each w i t h a s i n g l e -segmented m a x i l l a r y p a l p , a p a i r of l a r g e toothed mandibles, a l a r g e a n t e r i o r labrum, and a t h i c k l y h a i r e d hypopharynx. The best s p e c i f i c c h a r a c t e r s of t h i s r e g i o n are o f f e r e d by the u n s c l e r o t i z e d area on the v e n t r a l s u r f a c e of the head, u s u a l l y r e f e r r e d to as the p o s t - g e n a l c l e f t . The shape of t h i s c l e f t v a r i e s from that of an i n v e r t e d "V" to a more rounded shape, and i s of great importance t a x o n o m i c a l l y (Wood et al. 1962). P a t t e r n s of c o l o r a t i o n on the head va r y q u i t e d i s t i n c t l y between s p e c i e s , and are of some taxonomic v a l u e . Mature l a r v a e can f u r t h e r be d i s t i n g u i s h e d by having a m i d - v e n t r a l p r o l e g j u s t behind the head, which i s armed w i t h a c i r c l e t of hooks and f u n c t i o n s as a h o l d f a s t . P o s t e r i o r l y , v e n t r a l to the anal opening, i s a r i n g of many r a d i a t i n g rows of hooks, the anal r i n g . The number of hooks i n each row of t h i s r i n g v a r i e s between s p e c i e s . These two h o l d f a s t s , the p r o l e g and a n a l - r i n g , are used by the l a r v a i n locomotion. Larvae can a l s o r e l e a s e themselves on s i l k threads produced by the s a l i v a r y glands, f o r attachment f u r t h e r downstream. The l a r v a l rectum bears prominent, c o l o u r l e s s r e c t a l g i l l s , b e l i e v e d to have an osmo-regulatory f u n c t i o n (Crosskey 1973). - 14 At m a t u r i t y the l a r v a possesses d i s t i n c t g i l l - s p o t s on the thorax, which are the f u t u r e pupal g i l l s . A l s o , the d o r s a l abdominal hooks of the f u t u r e pupa show through the l a r v a l c u t i c l e . P r i o r to pupation a cocoon i s c o n s t r u c t e d from s i l k produced by the s a l i v a r y g lands. The shape of the cocoon v a r i e s between the d i f f e r e n t s p e c i e s . A c c o r d i n g to Crosskey (1973), some ve r y r a r e forms have no cocoons at a l l . At t h i s stage the arrangement of the abdominal hooks on the pupa, and the form of the pupal g i l l s i s of gre a t taxonomic importance. The number of r e s p i r a t o r y f i l a m e n t s i n each g i l l i s g e n e r a l l y c o n s t a n t i n each s p e c i e s , and may range between 4 to 60 i n d i f f e r e n t s p e c i e s (Malloch 1914). 1.1.3 Egg morphology B l a c k f l y eggs are t y p i c a l l y smooth, o v o i d i n shape, white when l a i d , becoming d a r k e r d u r i n g embryogenesis. The l o n g a x i s ranges from 0.1 to 0.4 mm. No s p e c i a l s t u d i e s have been made on egg morphology but they are known to be r e l a t i v e l y r e s i s t a n t to chemical i n s e c t i c i d e s . 1.2 REPRODUCTION, GROWTH AND "MORPHOGENESIS 1.2.1 Reproduction The mating process o f a d u l t b l a c k f l i e s i s d e a l t w i t h v e r y b r i e f l y i n the l i t e r a t u r e , and there i s no c l e a r u nderstanding of how or when mating o c c u r s . Presumably there i s a c e r t a i n time p e r i o d , which has yet to be d e f i n e d , i n which the newly emerged f l i e s undergo the necessary gonad development p r i o r to mating. - 15 -I t i s r e c o g n i s e d t h a t most, i f not a l l , o f the b l o o d -sucking s p e c i e s o f b l a c k f l i e s need a blood meal be f o r e o v i p o s i t i o n can occur. However, female f l i e s do not u s u a l l y suck b l o o d u n t i l 24-48 hours a f t e r emergence as i t takes t h i s time f o r the s a l i v a r y gland contents to accumulate. Many r e p o r t s have been made of swarms o f b l a c k f l i e s f l y i n g great d i s t a n c e s to t h e i r h o s t s , w i t h no s u g g e s t i o n t h a t the female r e t u r n s to i t s . r i v e r of o r i g i n f o r o v i p o s i t i o n . Presumably, when such swarming o c c u r s , the immigrant g r a v i d females d e p o s i t t h e i r eggs i n the n e a r e s t stream or r i v e r . One i n f e r e n c e might be that w h i l e l a r g e numbers swarm, a c e r t a i n percentage o f an emerging a d u l t p o p u l a t i o n remains around the i n f e s t e d stream where they reproduce and perpetuate a r e s i d e n t p o p u l a t i o n . However, t h i s a s p e c t , although v i t a l f o r understanding the b i o l o g y of the b l a c k f l y , has been almost completely by-passed to date. Fredeen (1963) suggested t h a t Simulium avotiaum can emerge e i t h e r as an autogenous or anautogenous p o p u l a t i o n , dependent on the month of development. I f e a r l y summer p o p u l a t i o n s do not r e q u i r e a b l o o d meal, as Fredeen suggests f o r Simulium avcticum3 then these ! autogenous females c o u l d account f o r the r e i n f e s t a -t i o n ' o f the b r e e d i n g s i t e which so f r e q u e n t l y occurs but i s without s u i t a b l e e x p l a n a t i o n . Once mating has o c c u r r e d the eggs are l a i d i n a s u i t a b l e a q u a t i c h a b i t a t , which may.be e i t h e r a stream or r i v e r a c c o r d i n g to the s p e c i e s . Eggs are u s u a l l y l a i d on t r a i l i n g v e g e t a t i o n i n the water or on submerged stones and r o c k s . C a r l s s o n (1962), s t u d y i n g the e g g - l a y i n g of Simulium venustum, Odagmia ornata and - 16 -Eusimulium aureum i n S c a n d i n a v i a , found a l l three s p e c i e s to d i s p l a y s i m i l a r p a t t e r n s o f o v i p o s i t i o n behaviour. The female f l i e s l a i d eggs on o b j e c t s at the water s u r f a c e , and a l s o climbed down underwater i n search of s u i t a b l e stones, sometimes to depths of 20 cm. Some b l a c k f l y s p e c i e s , such as Simulium vulgave and Simulium avctieum, are b e l i e v e d to d e p o s i t t h e i r eggs l o o s e l y and s i n g l y by f l y i n g low over the water s u r f a c e ( C a r l s s o n 1962, Fredeen et al. 1951). E x a c t l y what means the b l a c k f l y uses to a t t a c h newly l a i d eggs to a substratum i s u n c l e a r . Information would be d e s i r a b l e , but p r e s e n t l y does not e x i s t , on the p o s s i b l e r e l a t i o n s h i p s between the mating and o v i p o s i t i o n and such v a r i a b l e s as l i g h t - i n t e n s i t y , r e l a t i v e humidity, temperature, and wind. 1.2.2 Morphogenesis and growth The development p e r i o d f o r b l a c k f l y eggs may vary from a few days to a few months depending on the s p e c i e s and the s i t u a -t i o n . Most workers agree, as might be expected, t h a t the l e n g t h of the egg stage depends upon temperature c o n d i t i o n s o f the stream or r i v e r . In the t r o p i c s eggs may develop i n one or two days, whereas many temperate s p e c i e s have egg stages l a s t i n g f o r p e r i o d s of up to s e v e r a l months. Some s p e c i e s are known to be able to develop from s u b - a r c t i c streams f r o z e n over f o r the winte r months. Egg diapause can a l s o occur (Crosskey 1973). The p e r i o d o f l a r v a l development i n v o l v e s e i g h t or nine i n s t a r s and v a r i e s g r e a t l y i n o v e r a l l d u r a t i o n . Crosskey suggests that l a r v a e o f northern c l i m a t e s , which over-winter and develop s l o w l y , produce l a r g e r a d u l t s than are found i n the t r o p i c s where - 17 -l a r v a l development i s r a p i d . The true pupal stage a l s o v a r i e s i n l e n g t h , but there appears to be some c o n f u s i o n over t h i s . Crosskey (1973) suggests that as the pupal l i f e i s always s h o r t , i t s development i s independent of temperature, but there seems to be no support i n the l i t e r a t u r e f o r t h i s assumption. In f a c t , Matheson (1950) r e p o r t e d the b l a c k f l y pupal stage as l a s t i n g from two to seven days, or l o n g e r , depending on the weather. Furthermore, C a r l s s o n (1962) found t h a t pupae of Simulium vulgave 3 Simulium venustum3 Simulium veptans 3 Wilhelmia equina and Odagmia ornata emerge'. \ sooner i n a warm stream than a c o o l one. C e r t a i n l y i t would seem t h a t Crosskey's statement must be questioned. Because the " t i m i n g " v a r i e s so g r e a t l y between s p e c i e s i t is common to have d i f f e r e n t s p e c i e s emerging almost c o n t i n u o u s l y , one s p e c i e s a f t e r the other, f o r the e n t i r e summer. The f a c t t h at the s p e c i e s are changing so f r e q u e n t l y has l e d to g r e a t c o n f u s i o n i n taxonomy and i n c l i n i c a l aspects o f s e n s i t i v i t y and immunity. 1.3 FEEDING ' , An understanding of the f e e d i n g a c t i v i t i e s and s p e c i f i c food of b l a c k f l i e s , i n both l a r v a l and a d u l t s t a g e s , i s necessary f o r i n t e r p r e t a t i o n of the ecology of the v a r i o u s s p e c i e s i n t h e i r d i f f e r e n t and r e g i o n a l h a b i t a t s . On t h i s b a s i s c a u s a l r e l a t i o n -s h i p s , p r e d i c t i o n s , and environmental m a n i p u l a t i o n s become p o s s i b l e . - 18 -1.3.1 L a r v a l f e e d i n g The d i e t o f b l a c k f l y l a r v a e i s somewhat i l l - d e f i n e d i n the l i t e r a t u r e , and t h i s aspect v e r y o b v i o u s l y needs c l o s e r study. Most workers r e f e r to l a r v a e f e e d i n g on " d e t r i t u s " , but few have d e f i n e d t h i s term. A c c o r d i n g to Jones (1949) , " D e t r i t u s means amorphous ve g e t a b l e matter mixed wi t h f i n e g r i t and o c c a s i o n a l l y w i t h a few empty a l g a l c e l l s " . Species that possess c e p h a l i c fans (most s p e c i e s ) are able to s t r a i n " p a r t i c u l a t e matter" from the water by h o l d i n g t h e i r fans out i n t o the c u r r e n t o f the water. The l a r v a e are de s i g n a t e d as f i l t e r f e e d e r s . The few s p e c i e s known to be without c e p h a l i c fans appear to feed by r a k i n g the s u b s t r a t e w i t h the labrum ( C r a i g 1974, Crosskey 1973). A d e t a i l e d study on i n g e s t e d food of the v a r i o u s s p e c i e s i n t h e i r d i f f e r e n t h a b i t a t s i s needed. 1.3.2 A d u l t f e e d i n g Knowledge of the f e e d i n g h a b i t s of a d u l t b l a c k f l i e s , and the environmental c o n d i t i o n s f a v o u r a b l e to o b t a i n i n g food, i s s u r p r i s i n g l y l a c k i n g f o r most s p e c i e s . The degree of dependency of b l a c k f l i e s on b l o o d as a n u t r i e n t source i s open to q u e s t i o n . C e r t a i n l y b l a c k f l i e s have been observed v i s i t i n g f l o w e r s , and bl o o d - s u c k i n g females have f r e q u e n t l y been found w i t h a c o l o u r l e s s sugary f l u i d s t o r e d i n the crop. I t i s not known how important blood i s to the v a r i o u s s p e c i e s , or how much the females r e l y on n e c t a r as a n u t r i e n t source. I t i s merely assumed that male b l a c k f l i e s feed on n e c t a r , no p r o o f appears to be a v a i l a b l e . B l a c k f l i e s feed on blood from a wide range of warm-blooded v e r t e b r a t e h o s t s . A v a i l a b l e f i e l d s t u d i e s suggest. *that the - 19 -m a j o r i t y of s p e c i e s show a d i s t i n c t p r e f e r e n c e f o r f e e d i n g e i t h e r on b i r d s ( o r n i t h o p h i l i c ) or on mammals (mammalophilic). No s p e c i e s i s known to feed e x c l u s i v e l y on humans. The degree of host s p e c i f i c i t y of b l a c k f l i e s i s not f u l l y understood, and many u n c e r t a i n t i e s e x i s t i n the o b s e r v a t i o n s r e p o r t e d so f a r . Problems a r i s e when assumptions are made on the host p r e f e r e n c e s of c e r t a i n s p e c i e s , when i n f a c t such apparent " p r e f e r e n c e s " are an a r t i f a c t of the circumstance that other hosts are l a c k i n g i n the study area. Some b l a c k f l y s p e c i e s d i s p l a y much more s p e c i f i c f e e d i n g h a b i t s than o t h e r s , p r e f e r e n c e s may a l s o d i f f e r f o r the same s p e c i e s i n d i f f e r e n t l o c a t i o n s ( F a l l i s 1964). A d e t a i l e d account' of theimpact of b l a c k f l i e s on t h e i r h o s t s , the range of hosts and consequent host r e a c t i o n s i s giv e n i n s e c t i o n 4. Feeding mechanism: The female mouth p a r t s , as p r e v i o u s l y d e s c r i b e d , are used to l a c e r a t e the s k i n of the h o s t , and to pr o v i d e an oozing r e s e r v o i r o f blood. During b i t i n g the s k i n i s f i r s t s t r e t c h e d taut by the toothed labrum, which appears to make p e n e t r a t i o n by the mandibles p o s s i b l e . The saw-toothed mandibles are worked i n t o the s k i n i n a s c i s s o r - l i k e manner, c u t t i n g a c r o s s the c a p i l l a r i e s i n a way which causes subcutaneous b l e e d i n g . The mandible p e n e t r a t i o n i s f o l l o w e d by the p i e r c i n g m a x i l l a e and hypopharynx. T h i s a c t i o n does not cause immediate p a i n , as does the p e n e t r a t i o n o f mosquito mouth p a r t s . Once the mouth p a r t s are f i r m l y i n s e r t e d , s a l i v a i s pumped down i n t o the wound from the s a l i v a r y glands, and blood i s drawn up. The amount o f blood taken at each meal i s e q u i v a l e n t to r a t h e r more - 20 -FIGURE 3. THE HEADS OF (A) A FEMALE AND (B) A MALE OF A SPECIES OF SIMULIUM, SHOWING THE MOUTH PARTS. (X30) FROM: C a r l s s G. (1962). 21 -than the body weight of the i n d i v i d u a l f l y (___ 2 mgm.). Co n t r a r y to popular b e l i e f , the f l i e s cannot b i t e r e p e a t e d l y , i n f a c t i t may take two to f o u r days f o r the s a l i v a r y glands to become recharged with s a l i v a a f t e r one b l o o d meal, and d u r i n g t h i s time blood i s excluded from the d i e t (Crosskey 1973, Davies and Peterson 1956). The s a l i v a i s g e n e r a l l y b e l i e v e d to c o n t a i n an a n t i c o a g u l a n t , the nature of which i s unknown, and an a g g l u t i n i n . However, d e t a i l e d s t u d i e s of the s a l i v a have been made f o r o n l y a few s p e c i e s of b l a c k f l i e s (Yang and Davies 1974). The c l i n i c a l d e t a i l s of b i t i n g , and the t o x i c r e a c t i o n so induced, w i l l be d i s c u s s e d i n d e t a i l i n s e c t i o n 4. 1.4 FLIGHT The f l i g h t a c t i v i t i e s of b l a c k f l i e s are almost t o t a l l y c o n f i n e d to the d a y l i g h t hours, p a r t i c u l a r l y 5 p.m. to 7 p.m. T h i s i s i n c o n t r a s t to mosquito behaviour, and furthermore, u n l i k e mosquitoes, b l a c k f l i e s o n l y r a r e l y f l y i n t o b u i l d i n g s . T h i s behaviour i s taken advantage of i n the p r a c t i c e of p r o v i d i n g dark s h e l t e r f o r c a t t l e . Because b l a c k f l i e s are on the wing out of doors d u r i n g d a y l i g h t working hours, very many outdoor, a c t i v i t i e s are s e r i o u s l y a f f e c t e d . F o r e s t a c t i v i t i e s are no e x c e p t i o n ; l a b o u r f o r c e e f f i c i e n c y i s h i t , group morale i s lowered, and some work o p e r a t i o n s may even have to be suspended or abandoned. The f l i g h t range of b l a c k f l i e s i s g r e a t l y i n f l u e n c e d by winds, and p o s s i b l y by air-movements, although very l i t t l e documentation e x i s t s . Simulium arcticum was r e p o r t e d f l y i n g i n - 22 -wind-borne swarms f o r 90 to 100 m i l e s (144 - 166 Km) i n the Saskatchewan V a l l e y and Simulium columbaschensis i s r e c o r d e d to have " t r a v e l l e d " 124-280 mi l e s (200 - 400 Km) w i t h wind c u r r e n t s on the Danube (Herms 1969). C e r t a i n l y , the f l i g h t range o f . b l a c k f l i e s seems to have great p o t e n t i a l when any wind i s i n v o l v e d . A v e r y important q u e s t i o n , which so f a r has not been i n v e s t i g a t e d , i s whether f l i g h t i s a necessary c o n d i t i o n e r f o r f e e d i n g and/or o v i p o s i t i o n , i n c o n f o r m i t y w i t h the p r i n c i p l e o f s u c c e s s i v e i n d u c t i o n , which has been shown to apply to o t h e r i n s e c t s (Graham 1959, Kennedy and Booth 1963). I f t h i s does apply to o t h e r i n s e c t s i t might w e l l e x p l a i n one of the problems encountered w i t h r e a r i n g b l a c k f l i e s i n the l a b o r a t o r y . Only one group o f workers has so f a r succeeded i n r e a r i n g b l a c k f l i e s throughout a complete c y c l e i n the l a b o r a t o r y (Wenk and Raybould 1972). P r e v i o u s l y , r e s e a r c h e r s have found i t i m p o s s i b l e to get newly emerged a d u l t f l i e s ( t h a t have been r e a r e d from eggs) to feed on b l o o d and to o v i p o s i t . No c o n s i d e r a t i o n has been g i v e n to a d u l t f l i g h t requirements i n any of these r e a r i n g experiments. T h i s aspect warrants p r e c i s e study b e f o r e one might hope to r e a r b l a c k f l i e s s u c c e s s f u l l y i n the l a b o r a t o r y . U n t i l l a b o r a t o r y r e a r i n g can be accomplished, p r o g r e s s w i l l be h i n d e r e d i n e x p e r i -mental work which r e q u i r e s that the age i n hours or days, or the biography o f the i n d i v i d u a l i n s e c t s be known. Fredeen (1963) has p o i n t e d out that Simulium aratioum does not appear to need any c o n d i t i o n i n g f l i g h t p r i o r to o v i p o s i t i o n i n i t s e a r l y summer p o p u l a t i o n , as these i n d i v i d u a l s are autogenous, and o v i p o s i t i o n - 23 -# occurs w i t h i n c l o s e p r o x i m i t y of the emergence area. However, i t may s t i l l be that i n d i v i d u a l s r e q u i r e a c e r t a i n p e r i o d o f short range f l i g h t around the r i v e r b e f o r e they are "ready" to o v i p o s i t . T h i s aspect has not been i n v e s t i g a t e d . 1.5 BEHAVIOUR A knowledge of the determinants of b l a c k f l y behaviour would p r o v i d e a f o u n d a t i o n f o r d e f i n i n g and p r e d i c t i n g the circumstances under which a t t a c k s may be expected to occur. A l s o , such knowledge would p r o v i d e an important key to techniques needed f o r r e a r i n g b l a c k f l i e s i n the l a b o r a t o r y . Furthermore, a knowledge of the components and determinants of behaviour would p r o v i d e the necessary b a s i s f o r d e s i g n i n g b i o a s s a y techniques f o r the development o f chemical a t t r a c t a n t s f o r use i n t r a p s , or r e p e l l e n t s f o r p r e v e n t i n g a t t a c k s on i n d i v i d u a l h o s t s . B e h a v i o u r a l s t u d i e s to date have f a i l e d to c o n s i d e r the numerous determinants which must be c o n s i d e r e d b e f o r e even the foundations o f behaviour can be understood. The study of b l a c k -f l y behaviour should i n v o l v e a c o n s i d e r a t i o n of the f o l l o w i n g determinants: -- The s p e c i e s under study must be known and c l a s s i f i e d without any doubt. R e s u l t s o b t a i n e d with one s p e c i e s cannot a u t o m a t i c a l l y be t r a n s f e r r e d to another. - A knowledge of the sex of the i n d i v i d u a l s under study, or the sex r a t i o , i s a l s o of uttermost importance i n any behaviour s t u d i e s . - Behaviour can a l t e r r a d i c a l l y with the age of the - 24 -i n d i v i d u a l s , t h e r e f o r e i t i s v i t a l to know the p h y s i o l o g i c a l age of the p o p u l a t i o n under study. - Quite o f t e n f l i e s used i n e i t h e r f i e l d or l a b o r a t o r y study have undergone some k i n d of " c o n d i t i o n i n g " p o s s i b l y by heat, c o l d or f l i g h t . T h i s p o s s i b i l i t y must be co n s i d e r e d when r e v i e w i n g the r e s u l t s o f any behaviour s t u d i e s . - Whether or not a b l a c k f l y has had i t s f i r s t blood-meal w i l l g r e a t l y a f f e c t the p a t t e r n of behaviour. A l s o , assuming the f l i e s have a l r e a d y sampled b l o o d , the time s i n c e the f l i e s l a s t f e d should be known. F l i e s i n • d i f f e r e n t s t a t e s of n u t r i t i o n d u r i n g a behaviour study cannot be f r e e l y compared. - I t may be th a t one response i s i n h i b i t e d by another, and that as Kennedy and Booth suggested f o r aphids (1963), one a c t i v i t y i s i n f l u e n c e d by the p r e v i o u s a c t i v i t y o f the i n s e c t . I f such a phenomenon occurs w i t h i n b l a c k f l y p o p u l a t i o n s i t has as yet to be r e c o g n i s e d , but the concept should not be ignored i n any behaviour study. - The ambient c o n d i t i o n s under which behaviour i s observed, e i t h e r i n the f i e l d or i n the l a b o r a t o r y , are the behaviour determinants t h a t have r e c e i v e d most a t t e n t i o n i n the l i t e r a t u r e . Behaviour i n r e l a t i o n to temperature, r e l a t i v e humidity, l i g h t i n g , and a i r flow has been s t u d i e d f o r some mosquitoes, but to a much l e s s e r degree f o r any s p e c i e s o f b l a c k f l y . U n f o r t u n a t e l y many of the experiments have f a i l e d to take note of the behaviour - 25 -determinants mentioned p r e v i o u s l y . - F u r t h e r , there are the host f a c t o r s to be taken i n t o account i n any study o f i n s e c t behaviour, and t h i s i s the most e x t e n s i v e l y worked f i e l d . The p h y s i o l o g i c a l s t a t e o f the host, the age, c o l o u r o f the s k i n , and s t a t e o f n u t r i t i o n may a l l i n f l u e n c e the behaviour of a b l a c k f l y . Too l i t t l e i s understood of the p o s s i b l e importance of s p e c t r a l r e f l e c t i o n and emission o f the s k i n , or o f the chemical products produced on the s k i n by sebaceous and sudoriparous glands. The mechanisms i n v o l v e d i n b r i n g i n g an a t t a c k i n g b l a c k f l y i n t o . c o n t a c t w i t h i t s host are among the most s i g n i f i c a n t o f the f a c t o r s i n the s u r v i v a l s t r a t e g y o f the a t t a c k e r , as w e l l as i n the consequences f o r the host. The most s t u d i e d area of b l a c k f l y behaviour i s that of host a t t r a c t i o n and host s e l e c t i o n by way of host f a c t o r s , and these experiments w i l l be reviewed here. However, i t must be remembered t h a t many of these behaviour experiments have ignored the other determinants o f behaviour s t a t e d p r e v i o u s l y . Although the h o s t - f i n d i n g procedure of b l a c k f l i e s i s not f u l l y understood, i t i s assumed t h a t the bl o o d - s e e k i n g females are a t t r a c t e d by both v i s u a l and a i r - b o r n e s t i m u l i . 1.5.1 V i s u a l host f a c t o r s of importance i n a t t r a c t i o n C o l o u r : L i t e r a t u r e p e r t a i n i n g to the d i f f e r e n t i a l l a n d i n g responses o f the Simuliidae to c o l o u r i s r e l a t i v e l y s c a r c e , (Davies 1951, 1961, 1972, r e l a t i n g to Simulium venustum; Fredeen 1961 r e l a t i n g to Simulium venustum S. decorum^ S. vittatum; - 26 -Bradbury and Bennett 1974 a) r e l a t i n g to seven s p e c i e s o f s i m u l i i d s . The work of Peschken and T h o r s t e i n s o n (1965) was concerned w i t h the a t t r a c t i o n o f g r a v i d female b l a c k f l i e s to o v i p o s i t i o n s i t e s , and such responses cannot be compared to the responses i n v o l v e d i n l a n d i n g to feed. Bradbury and Bennett's work (1974 a)) i n d i c a t e d t h a t s p e c i e s emerging i n the s p r i n g have c o l o u r p r e f e r e n c e s d i f f e r i n g from those s p e c i e s emerging i n the summer. I t should be noted that background c o l o u r s o f the environment, o f f e r i n g e i t h e r host c o n t r a s t or host cover, change through the seasons, and a c o l o u r imposing an obvious c o n t r a s t i n g s p e c t r a l composition i n the s p r i n g may blen d w i t h the background environment by the summer. Davies (1951, 1961, 1972) found t h a t l a n d i n g frequency o f b l a c k f l i e s v a r i e d i n v e r s e l y w i t h the i n t e n s i t y of r e f l e c t e d l i g h t . Dark c l o t h s , w i t h the h i g h e s t r e f l e c t a n c e of u l t r a -v i o l e t and v i o l e t wave-lengths, had the h i g h e s t " l a n d i n g percen-tages". I t i s worth n o t i n g t h a t Davies used two p i e c e s o f paper or c l o t h , s i d e by s i d e , f o r each of h i s experiments. I t i s h i g h l y p o s s i b l e that one c o l o u r c o u l d a f f e c t the a t t r a c t a n c y of the oth e r i n such a s i t u a t i o n . A l s o , he used 6" x 6" squares f o r a l l of h i s sample c o l o u r s , so i g n o r i n g the p o s s i b i l i t y t h a t s i z e o f t a r g e t c o l o u r c o u l d i n f l u e n c e the r e s u l t s . The c o l o u r s l e a s t frequented by b l o o d - s e e k i n g s i m u l i i d s are those t h a t are found most a t t r a c t i v e to o v i p o s i t i n g females (Peschken and T h o r s t e i n s o n 1965). I t i s p o s s i b l e t h a t the pr e f e r e n c e f o r y e l l o w and green d i s p l a y e d d u r i n g o v i p o s i t i o n may occur around the host a f t e r the females have had t h e i r f i r s t blood meal. - 27 Davies draws a comparison between h i s 1972 r e s u l t s f o r s i m u l i i d c o l o u r p r e f e r e n c e and the r e s u l t s of Brown (1956) f o r mosquito c o l o u r p r e f e r e n c e , as the same m a t e r i a l s dyed to the same standard c o l o u r s were used, t o g e t h e r with the same s p e c t r o photometer. He notes that the order of a t t r a c t i o n of c o l o u r s f o r female Aedes aegypti d i f f e r e d from t h a t f o r Simulium venustum, although, f o r both, the green, y e l l o w and red were the l e a s t frequented, and dark p u r p l e and dark red the. most. Not a l l such experiments can be so r e a d i l y compared. I t must be remembered that measurements of t o t a l i n t e n s i t y f o r one c o l o u r w i l l d i f f e r i f a photometer more s e n s i t i v e to c e r t a i n wave-lengths i s used. In Davies' (1951) e a r l y work, r e f l e c t a n c e was measured with an exposure meter c a r e f u l l y s e l e c t e d f o r i t s s e n s i t i v i t y s i m i l a r to the human eye, and yet i t was i n s e c t v i s i o n under t e s t , not human. Although red and blue are a p p a r e n t l y more a t t r a c t i v e than b l a c k f o r mammalophilic s i m u l i i d s , Bennett et al. (1972) noted t h a t Simulium euryadminioulum s e l e c t e d b l a c k " c o l o u r s " , but then t h i s s p e c i e s of b l a c k f l y i s a t t r a c t e d to o n l y one host, as f a r as i s known, and the host's n a t u r a l c o l o u r i s dark. Although the most r e c e n t r e s u l t s on c o l o u r p r e f e r e n c e s (Bradbury and Bennett 1974 a)) conform with the g e n e r a l c o n c l u -sions of the e a r l i e r workers, the need f o r d e t a i l e d c o n s i d e r a t i o n of behaviour on a s p e c i e s l e v e l i s s t r o n g l y emphasized. The b e h a v i o u r a l s t a t e and p h y s i o l o g i c a l age of the f l i e s under study must always be borne i n mind. The behaviour of a female b l a c k f l y may i n v o l v e q u i t e d i f f e r e n t c o l o u r responses before and a f t e r - 28 -b l o o d - f e e d i n g . I t should be s t r e s s e d that g e n e r a l i z a t i o n s on the a t t r a c t i v e n e s s o f c o l o u r s to s i m u l i i d s , when regarded c o l l e c -t i v e l y , must be t r e a t e d w i t h c a u t i o n . As yet there i s no p r o o f that b l a c k f l i e s can p e r c e i v e " c o l o u r s " at a l l . I f c l o t h i n g c o l o u r i s chosen and worn f o r i t s u n a t t r a c t i v e -ness to b l a c k f l i e s , the exposed areas such as the fa c e and hands, may, by reason of simultaneous c o n t r a s t , become that much more a t t r a c t i v e . While swarms of f l i e s might be a t t r a c t e d t o , and r e s t on, the back of a dark r e d j a c k e t , a l e s s a t t r a c t i v e c o l o u r would leave the f l i e s to f i n d an a l t e r n a t i v e l a n d i n g s i t e such as the face or hands, which would a l s o p r o v i d e the d e s i r e d f e e d i n g s i t e s . Shape, movement^and contour: The v i s u a l f a c t o r s of shape, movement and contour have been shown to have some importance i n the a t t r a c t a n c y o f c e r t a i n b l a c k f l y and mosquito s p e c i e s to t h e i r h o s t s . S i p p e l l and Brown (1953) demonstrated t h a t a t t r a c -t i o n o f Aedes aegypti to p r a i r i e deer mice (under l a b o r a t o r y c o n d i t i o n s ) was doubled i f the mice were allowed to move f r e e l y , r a t h e r than being c o n f i n e d . S i m i l a r r e s u l t s were ob t a i n e d f o r d u l l b l a c k c a n i s t e r s when compared i n a s t a t i o n a r y p o s i t i o n or when moved along a s t r a i g h t l i n e . I t appeared from these experiments t h a t , under l a b o r a t o r y c o n d i t i o n s , v i s u a l were about equal to a i r b o r n e f a c t o r s i n a t t r a c t i v e n e s s f o r a s t i l l h o s t , but f o r a mobile host v i s u a l was the more "po w e r f u l " a t t r a c t a n t f a c t o r . For both inanimate and animate b o d i e s , these experiments i n d i c a t e d a d o u b l i n g of a t t r a c t a n c y w i t h movement. However, Wood and Wright (1968) co u l d not agree that movement c o n t r i b u t e d - 29 -any more than m a r g i n a l l y to the a t t r a c t i o n of Aedes aegypti i n the l a b o r a t o r y . The f i r s t work done on the a t t r a c t i o n of b l a c k f l i e s to moving o b j e c t s d i d not appear to agree with the above r e s u l t s (Peschken and T h o r s t e i n s o n 1965). However, these b l a c k f l y behaviour experiments d i d not i n v o l v e any n a t u r a l h o s t s , the f l i e s i n the experiments being a t t r a c t e d to t r a p s t h a t were hung i n a f i x e d p o s i t i o n as w e l l as some being hung f r e e l y to r o t a t e i n the a i r c u r r e n t s . The s t a t i o n a r y c y l i n d e r s a t t r a c t e d s i g n i f i -c a n t l y more f l i e s than the f r e e l y suspended ones. The need f o r f u r t h e r r e s e a r c h on the involvement of host movement i n a t t r a c t i o n i s e v i d e n t . Host shape i n r e l a t i o n to a t t r a c t a n c y of b l a c k f l i e s has been s t u d i e d to a somewhat g r e a t e r extent than has movement (Bennett et al. 1972, Fredeen 1961). Fredeen compared three t r a p shape designs f o r b l a c k f l i e s . The l a r g e s t , a "cow" s i l h o u e t t e t r a p was 4.feet (122 cm) h i g h , 5 f e e t (152.5 cm) long, and 2 f e e t (61 cm) wide, st a n d i n g on four wooden le g s and covered i n the upper t w o - t h i r d s w i t h dark brown plywood. The "sheep" s i l h o u e t t e t r a p was c o n s t r u c t e d 18 inches (45.8 cm) h i g h , 2 f e e t (61 cm) long and 1 f o o t (30.5 cm) wide. The t h i r d t r a p was a "pyramid" s i l h o u e t t e , 4 f e e t (122 cm) h i g h and 3 f e e t (91.5 cm) square. No b a i t was used i n the t r a p s and i t was found that Simulium arotioum, under f i e l d c o n d i t i o n s , was not i n f l u e n c e d i n i t s l a n d i n g responses by the shape of the t r a p s . However, i t appeared that the e f f e c t i v e n e s s of the t r a p s was a d i r e c t f u n c t i o n of s u r f a c e area and s i z e of opening on the 30 -underside of the t r a p , r e g a r d l e s s of shape. These 3 types of t r a p were p l a c e d very c l o s e l y t o g e t h e r d u r i n g the experiments, and t h i s f a c t o r may w e l l have i n f l u e n c e d the r e s u l t s . The a t t r a c t a n c y of a host may be i n f l u e n c e d by i t s contour. S i p p e l l and Brown (1953) compared the l a n d i n g r a t e s of Aedes aegypti on an a l l b l a c k cube and on a s e r i e s of b l a c k and white cubes. I t was found t h a t the a t t r a c t i v e n e s s of the b l a c k and white cubes c o u l d be i n c r e a s e d by as much as 60 p e r c e n t by i n c r e a s i n g the contour, i . e . by i n c r e a s i n g the number of squares on the cubes w h i l e keeping the areas of b l a c k and white equal (Brown 1956). Brown (1952) found t h a t s i g n i f i c a n t l y more mosquitoes were a t t r a c t e d to a g l o s s y b l a c k s u r f a c e than to a d u l l b l a c k one. He a t t r i b u t e d t h i s to the m i r r o r i n g s u r f a c e s p r e s e n t i n g an a t t r a c t i v e f l i c k e r e f f e c t to the i n s e c t s ' compound eyes. Peschken and T h o r s t e i n s o n (1965) compared the a t t r a c t i v e n e s s of 2-and 3-dimensional t a r g e t s to three b l a c k f l y s p e c i e s , but none of the s p e c i e s appeared able to d i s t i n g u i s h between the d i f f e r e n t t a r g e t s . However, Simulium euryadminioulum, the b l a c k f l y s p e c i f i c to the common loo n , has shown a d e f i n i t e p r e f e r e n c e f o r b l a c k t a r g e t s of 3-dimensional form r a t h e r than 2. I t may be t h a t t h i s s t r o n g response to 3-dimensional b l a c k i s a n a t u r a l response of the f l i e s to t h e i r h o s t s , remembering t h a t S. euryadminioulum i s an unusual s p e c i e s i n i t s t o t a l r e s t r i c t i o n to one host, the common loon. Bennett et al. 1972 a l s o found that t h i s b l a c k f l y p r e f e r r e d the most pronounced p o r t i o n s of any s i l h o u e t t e shape o f f e r e d . - 31 It would seem v i r t u a l l y i m p o s s i b l e to draw any c o n c l u s i o n s on the importance of host shape to b l a c k f l i e s from the experimen-t a l work done so f a r . For one s p e c i e s (S. euryadminiculum) shape/dimension does appear to have some r e l e v a n c e , but t h i s cannot be confirmed by workers who have t e s t e d Simulium venustum,. S. decorum or S. vittatum (Peschken and T h o r s t e i n s o n 1965). 1.5.2 A i r b o r n e host f a c t o r s of importance i n a t t r a c t i o n . Temperature and moisture: In 1910 Howlett conducted a s e r i e s of very simple experiments on some Indian s p e c i e s of mosquitoes, and was able to demonstrate the importance of c o n v e c t i v e heat i n the process of a t t r a c t i o n . He d i d t h i s by suspending a t e s t - t u b e of warm water above and below a cage of mosquitoes. The f l i e s were a t t r a c t e d o n l y when the tube was h e l d below them, so t h a t they were i n the c o n v e c t i v e c u r r e n t s emitted from i t . These r e s u l t s were l a t e r confirmed by Peterson and Brown (1951) , whose experiments i n v o l v e d the s e p a r a t i o n o f r a d i a t i o n and c o n v e c t i o n c u r r e n t s by the i n t e r p o s i t i o n of an a i r -t i g h t window of t h a l l i u m bromiodide between a warm o b j e c t and the t e s t mosquitoes. Without t h i s window, b i l l i a r d b a l l s warmed to 100 or 110°F (39 or 43°C) a t t r a c t e d twice as many f l i e s as b a l l s at 80°-90°F (27-32°C). At temperatures of 120°F (50°C) t h i s a t t r a c t i v e n e s s was r e v e r s e d . However, when the c o n v e c t i v e c u r r e n t s were shut out by the p o s i t i o n i n g of a t h a l l i u m bromiodide window, t h i s temperature response was e l i m i n a t e d , t h e r e f o r e suggesting that mosquitoes respond to c o n v e c t i v e and not r a d i a n t heat. - 32 S i m i l a r temperature s t u d i e s were conducted i n the f i e l d u s i n g robots as the a t t r a c t i v e b a i t (Brown 1951). The number of land i n g s per minute on the robots c l o t h i n g was taken as the c r i t e r i o n of a t t r a c t i v e n e s s . The robots were simple w a t e r - f i l l e d tanks on l e g s , one o f which was maintained at body temperature (37.5°C), while the other was f i l l e d w i t h c o l d water 48-64°F (9-18°C). Only when the c o o l e r robot was below 60°F (15.6°C) d i d the warmer a t t r a c t s i g n i f i c a n t l y more f l i e s . However, when the c l o t h i n g o f the warmer robot was moistened, and the tempera-, t u r e d i f f e r e n t i a l so i n c r e a s e d , the robot became n e a r l y twice as a t t r a c t i v e as the c o o l e r one. These experiments i n d i c a t e d t h a t warmth was a s i g n i f i c a n t f a c t o r i n a t t r a c t a n c y o n l y when the a i r temperature was below. 60°F (15.6°C). Above t h i s temperature moisture appeared to be needed f o r the warmer body to show any g r e a t e r a t t r a c t a n c y . These r e s u l t s d i s a g r e e w i t h those o b t a i n e d i n the b i l l i a r d b a l l experiments when the warmer b a l l was a l s o more a t t r a c t i v e , up t o 110°F (43°C). Brown's experiments c o n t i n u e d w i t h t e s t s on the a t t r a c t i o n of the human hand at d i f f e r e n t temperatures (Smart and Brown 1956). Only a v e r y narrow temperature range was used, the s u b j e c t s * hands not v a r y i n g more than 4°C. A hand t h a t was c o o l e d to 22°C (71°F) a t t r a c t e d s i g n i f i c a n t l y fewer f l i e s than a hand at normal body temperature. Although the warmer hand o f each p a i r used i n each t e s t was always the more a t t r a c t i v e , the r e s u l t s were not as h i g h l y p o s i t i v e as those o b t a i n e d w i t h the b i l l i a r d b a l l experiments. I t appears t h a t the " b e s t " r e s u l t s i n temperature d i f f e r e n c e experiments are o b t a i n e d when normal body-- 33 -temperature attractancy is compared with that of a super-cooled body. Also, the heating of a hand above body temperature decreases i t s attractancy when compared with a normal hand. It i s not easy to draw conclusions from these experiments. Generally, i t appears that temperature is of second place importance to moisture, and only when a dry body i s cooled does at t r a c t i o n seem to a l t e r at a l l . The combination of warmth plus moisture in a b a i t , which i s i n fact the most l i k e l y f i e l d s i t u a -t i o n , i s s i g n i f i c a n t l y more a t t r a c t i v e than a dry and warm b a i t . The f i r s t work on b l a c k f l y a t t r a c t i o n and the thermal question was that of F a l l i s et al. (1967). They noted that f l i e s were taken in greatest numbers in fan traps during the 5 p.m. -7 p.m. period. By adding heat to the fan traps they aimed to test the e f f e c t s of heat on attractancy, but the r e s u l t s are unreliable as a constant amount of heat was not maintained. Together with the thermal stimulus, carbon dioxide (CC^) was added to the traps, and the r e s u l t s suggested that more f l i e s were attracted, but t h i s did not hold for a l l the species tested. No generalizations are warranted u n t i l extensive work has been done on additional species. From the experiments performed with a i r streams in the laboratory (Brown et al. 1951), and with wet and dry b i l l i a r d b a l l s in the laboratory (Peterson and Brown 1951) , as well as with robots in the f i e l d (Brown 1951), i t would appear that moisture i s an important a t t r a c t i v e factor to Aedes aegypti. Moisture, however, took second place to temperature when ambient a i r temperatures f e l l below 60°F (Brown 1951, 1952, 1966). - 34 -Researchers s t u d y i n g the human hand (Smart and Brown 1966) were s u r p r i s e d to f i n d t h a t hands wi t h g r e a t e r water output were l e s s a t t r a c t i v e than the normal. T h i s was l a t e r confirmed w i t h a l a r g e number of s u b j e c t s (Brown 1966). No e x p l a n a t i o n was o f f e r e d at the time f o r the apparent divergence i n r e s u l t s . However, i t i s known that sudoriparous type sweat, such as that o c c u r r i n g on the hands, i s s i g n i f i c a n t l y l e s s a t t r a c t i v e than the sebaceous type of under-arm sweat. I t c o u l d have been a combination o f water vapour and c o n s t i t u e n t s o f sweat t h a t r e s u l t e d i n the r e p e l l e n c y r e p o r t e d i n Smart and Brown's work with the human hand, i n f a c t they suggested f a c t o r s other than, but r e l a t e d t o , moisture output. The r e s u l t s of moisture a t t r a c t i v e n e s s experiments on a hand cannot be taken as any r e a d i n g of the importance o f moisture f o r the human body as a whole. Sweat: The importance of sweat i n a t t r a c t a n c y has not yet been s a t i s f a c t o r i l y d e f i n e d . Parker (1948) found arm-pit sweat to be more a t t r a c t i v e to Aedes aegypti than moisture a l o n e . W i l l i s (1947) and Brown et al. (1951) agreed w i t h t h i s r e s u l t . However, these i n i t i a l experiments met w i t h c o n t r a d i c t i o n , as does the whole s u b j e c t of sweat today. E a r l i e r workers (Crumb 1922, Rudolfs 1922) u s i n g Aedes solioitans and Reuter (1936) working on Anopheles atroparvus, a l l agreed that sweat, e i t h e r arm-pit sebum or forehead sudor, d i d not show any s i g n i f i c a n t a t t r a c t a n c y to mosquitoes. Brown (1951) conducted a s e r i e s of f i e l d experiments u s i n g robots as b a i t s . He n o t i c e d t h a t robots dressed i n sweaty j e r k i n s (arm-pit sweat) a t t r a c t e d more f l i e s than robots i n c l e a n - 35 c l o t h i n g of s i m i l a r moisture content. F u r t h e r l a b o r a t o r y experiments (Brown et al. 1951) i n d i c a t e d t h a t human arm-pit sweat was r e p e l l e n t at h i g h c o n c e n t r a t i o n s and a t t r a c t i v e at low, when i t s vapour was passed through an o l f a c t o m e t e r . However, i t c o u l d be questioned whether they were o b s e r v i n g r e p e l l e n c e or a r r e s t a n c e . It i s known t h a t arm-pit and forehead sweat d i f f e r i n t h e i r chemical make-up, p a r t i c u l a r l y i n the sudor/sebum balance. Sudor i s an aqueous s o l u t i o n of NaCl p l u s n o n - c o l l o i d a l o r g a n i c compounds prese n t i n the b l o o d , and i s produced a l l over the body s u r f a c e , p a r t i c u l a r l y i n h a i r l e s s r e g i o n s such as the palms, s o l e s and forehead. Sebum c o n t a i n s lower f a t t y a c i d s , e s t e r s of h i g h e r a l c o h o l s , c h o l e s t e r o l , and albumin, and i s produced mainly i n the underarm and g r o i n r e g i o n s . Thompson and Brown (1955) deci d e d to look i n t o the d i f f e r e n c e s i n a t t r a c t a n c y of sudoriparous and sebaceous sweat. A f t e r a s e r i e s of o l f a c t o m e t e r experiments, they concluded t h a t although arm-pit sweat d i d appear a t t r a c t i v e at c e r t a i n c o n c e n t r a t i o n s , forehead sweat was not a t t r a c t i v e at a l l . They were not able to i n c r e a s e the a t t r a c t a n c y of moist c l o t h i n g by the a d d i t i o n of arm-pit sweat, thereby c o n t r a d i c t i n g the e a r l i e r r e s u l t s of Brown (1951) wi t h the r o b o t s . Observations made by v a r i o u s workers on the a t t r a c t a n c y of sweat are so c o n t r a d i c t o r y that i t i s obvious that the problem i s a complex one needing deeper understanding. I t appears t h a t there i s o n l y a vague understanding of body s u r f a c e e x c r e t i o n s and s e c r e t i o n s . For example, Brown and Carmichael (1961) suggest that "body odour" a t t r a c t a n c y may be due to a t t r a c t a n t s such as 36 -amino a c i d s , d i f f u s i n g d i r e c t l y from the s k i n c a p i l l a r i e s . T h i s s u g g e s t i o n seems h i g h l y u n l i k e l y as amino-acids are not known to occur on the s k i n , apart from when they are e x c r e t e d by sweat glands which occur a l l over the body s u r f a c e . With r e g a r d to the i n d i v i d u a l amino-acids found i n body sweat, i t would appear that some a t t r a c t w hile others r e p e l (Hier et al. 1946). I n t e r e s t has centered around l y s i n e and a l a n i n e as a t t r a c t i v e components (Brown 1956, Brown and Carmichael 1961, L i p s i t z and Brown 1964, Skinner et al. 1965). Brown and Carmichael c o n s i d e r l y s i n e to be more important than a l a n i n e . The g e n e t i c a l l y determined b a s i c body chemistry of an i n d i v i d u a l w i l l determine i n d i v i d u a l body emanations and odour. Odour w i l l d i f f e r between i n d i v i d u a l s , and t h i s may w e l l a f f e c t a t t r a c t a n c y . I t i s a l s o q u i t e p o s s i b l e that body emanations of an i n d i v i d u a l w i l l change wi t h change i n d i e t , and consequently a t t r a c t a n c y may a l t e r . The s u b j e c t of d i e t a f f e c t i n g body emanations, and t h e r e f o r e a t t r a c t a n c y , has not been gi v e n the c o n s i d e r a t i o n i t warrants. The whole q u e s t i o n of body emanations and b i t i n g f l y a t t r a c -tancy r e q u i r e s e x perimentation and understanding by persons competent i n t h i s f i e l d . It i s not s u f f i c i e n t f o r e n t o m o l o g i s t s to conduct s m a l l - s c a l e experiments on the importance of sweat i n a t t r a c t a n c y when they do not have even the vaguest understan-ding of body emanations. Human p h s y i o l o g i s t s , working t o g e t h e r with i n s e c t b e h a v i o u r i s t s , are needed i f t h i s f i e l d i s to be worked and understood. The work done by e n t o m o l o g i s t s to date, i f having done nothing e l s e , has r e v e a l e d the p r e s e n t - 37 c o n f u s i o n and l a c k of understanding, and has p o i n t e d the d i r e c t i o n f o r f u t u r e r e s e a r c h . Carbon d i o x i d e : One of the most c o n t r o v e r s i a l m a t e r i a l s i n the study of a t t r a c t i o n i s carbon d i o x i d e . Some workers have found i t to a t t r a c t mosquitoes (Brown 1951, 1956), while o t h e r s have found i t to r e p e l (Brouwer 1960, W i l l i s and Roth 1952). Va r i o u s experiments w i t h o l f a c t o m e t e r s have gi v e n q u i t e c o n t r a -d i c t o r y r e s u l t s . Brown et al. 1951 showed dry a i r w i t h 10 per cent CO2 to be more a t t r a c t i v e to Aedes aegypti than dry a i r alone, and yet moist a i r w i t h 10 percent CO2 was no more a t t r a c -t i v e . W i l l i s and Roth (1952) used both l a r g e and small cage • o l f a c t o m e t e r s , and i n the former the a d d i t i o n of t e n p e r c e n t CO£ had a r e p e l l e n t e f f e c t . Many workers agree today t h a t the r o l e of CO2 i s t h a t of a g e n e r a l a c t i v a t o r , r a t h e r than an o r i e n t a t o r ( F a l l i s et al. 1967, Hocking 1971). The g e n e r a l t r e n d of r e s u l t s suggest t h a t a l t h o u g h CO2 may a c t i v a t e at low c o n c e n t r a t i o n s , i t can a l s o " r e p e l " at higher ones. I t should be noted that under the c o n d i t i o n s of t h e i r o l f a c t o m e t e r s i t i s p o s s i b l e t h a t the experimenters m i s i n t e r p r e t e d the e f f e c t s , and f a i l e d to r e c o g n i s e that what they c a l l , " r e p e l l e n c e " may i n f a c t be a f l i g h t ' a r r e s t a n t t h a t leads to " l a n d i n g " . S p e c i f i c s i m u l i i d a t t r a c t i o n to CO2 has r a r e l y been found. The r e s u l t s of F a l l i s et al. 1967 support the idea that CO2 p l u s v i s u a l s t i m u l i a f f e c t s the movement of Simulium venustum toward t e s t s i l h o u e t t e s . In c o l l e c t i n g s e v e r a l s p e c i e s of b l a c k f l i e s , with the a i d of d i f f e r e n t s t i m u l i , F a l l i s et al. suggested an 38 -arrangement of the s p e c i e s i n t o four groups. The f i r s t group i n c l u d e s f l i e s t h a t w i l l move to an odour without added CC^, but more are a t t r a c t e d i f CC^ i s added. S. euryadminioulum i s the only s p e c i e s known to respond i n t h i s way. The second grouping i n c l u d e s f l i e s such as S. rugglesi, that come to CO,,, or C 0 2 p l u s an odour alone ( F a l l i s and Smith 1964). The t h i r d grouping i n v o l v e s those s p e c i e s t h a t move to CO2 alone, i . e . S. venustum. F i n a l l y , the f o u r t h group i n c l u d e s those s p e c i e s t h a t appear to r e a c t to v i s u a l s t i m u l i , but not to C O 2 . T h i s group system i s based on a minimum of evidence, and such e x t e n s i v e g e n e r a l i z a t i o n s seem somewhat unwarranted. F u r t h e r work needs to be done wi t h other s p e c i e s t a k i n g f u l l account of a l l p r e v a l e n t c o n d i t i o n s . G o l i n i and Davis (1971) performed upwind o r i e n t a t i o n behaviour experiments w i t h S. venustum i n the f i e l d . They found that S. venustum w i l l f l y upwind towards a source of C O 2 , and w i l l do so o n l y when t h i s gas i s p r e s e n t . (This supports the l a b o r a t o r y r e s u l t s of F a l l i s et al. 1967). Very recent work by Bradbury and Bennett (1974 b)) examines how v i s i o n and odour i n t e r a c t to a f f e c t the near range o r i e n t a t i o n and l a n d i n g of s i m u l i i d s . The experiments i n v o l v e d seven d i f f e r e n t b l a c k f l y s p e c i e s , although S. venustum was s t u d i e d most c l o s e l y . In summarizing the r e s u l t s they d e f i n e d three h i e r a r c h i c a l zones of o r i e n t a t i o n mechanisms, c o r r e s p o n d i n g to the sensory i n p u t s through which they are mediated. The f i r s t , long-range o r i e n t a t i o n , i n v o l v e s host s p e c i f i c odours, i . e . S. euryadminioulum. The second, middle-range o r i e n t a t i o n , occurs at the d i s t a n c e at which C 0 7 i n i t i a t e s a more p r e c i s e response - 39 -f o r most s i m u l i i d s . The t h i r d , c l o se-range o r i e n t a t i o n , i n v o l v e s c o l o u r response, s i z e of host, shape, movement, e t c . , CO- i n v o l v e ment being q u e s t i o n a b l e . The f i n a l c o n c l u s i o n drawn from t h i s work was t h a t C O 2 does act as an a c t i v a t o r of more p r e c i s e o r i e n t a t i o n f o r most s i m u l i i d s , but only at a d i s t a n c e termed "middle-range" (beyond 180 cm). More d i r e c t e d v i s u a l responses appear to occur at c l o s e range to the host. I f these r e s u l t s are taken as a g e n e r a l i z a t i o n of the r o l e of C O 2 i n b i t i n g f l y o r i e n t a t i o n , i t may help to e x p l a i n , i n p a r t , the g r e a t d i s c r e p a n c i e s i n past r e s u l t s when d i s t a n c e from the host to the f l i e s under study was not given any great c o n s i d e r a t i o n . Scanning e l e c t r o n microscope work (Mercer and Mclver 1973 a has r e v e a l e d the presence of bulb organs i n a sensory p i t on segment three of the p a l p s of f o u r s p e c i e s of b l a c k f l i e s . The s i g n i f i c a n c e of these f i n d i n g s i s that such s e n s i l l a have been found p r e v i o u s l y on other Nematocera, and are known to be s e n s i -t i v e to C 0 2 ( B a s s l e r 1958, K e l l o g 1970). I t would seem c r e d i b l e t h at the bulb organs on b l a c k f l y p a l p s would have a s i m i l a r f u n c t i o n . When the a d u l t b l a c k f l y i s i n f l i g h t the p a l p s are h e l d i n such a way as to expose the sensory p i t s to the oncoming a i r - s t r e a m , and the " C O 2 r e c e p t o r s " (the bulb organs) would appear to be i n an i d e a l p o s i t i o n f o r r e c e p t i o n of odours. For the three s p e c i e s of b l a c k f l y examined, a p a t t e r n i s c l e a r l y demonstrated with regard to the number of s e n s i l l a and the s p e c i e s ' c h a r a c t e r i s t i c behaviour. The two s p e c i e s , S. vuggiesi and S. venustum, both known to feed on blood, have s i g n i f i c a n t l y more bulb organs than S. baffinense, which does not take b l o o d . 40 -A l l of the male b l a c k f l i e s examined had co n s i d e r a b l y fewer sens i l i a than the females. Although b l a c k f l y a t t r a c t i o n cannot be reviewed f u l l y without c o n s i d e r i n g the extensive stud i e s on mosquitoes, i t must be emphasized that what appears true f o r any mosquito cannot be t r a n s f e r r e d i n t o a g e n e r a l i z a t i o n f o r b l a c k f l i e s . Very many of the behaviour experiments to date have been conducted i n the l a b o r a t o r y , under unnatural c o n d i t i o n s and on unnatural hosts. For example, most of the experiments designed to t e s t the importance of CC^ i n a t t r a c t a n c y were based on CC^ concentrations o f 10 percent and g r e a t e r , when, i n f a c t , l e s s than 3 percent CC^ i s expired i n the human breath. Results achieved are taken to i n d i c a t e the r e l a t i v e importance of v a r i o u s s t i m u l i t e s t e d , but the value of such r e s u l t s i s i n doubt when so many f a c t o r s are o b v i o u s l y ignored. Experiments i n v o l v i n g d i f f e r e n t c o n d i t i o n s of temperature or humidity may e l i c i t t o t a l l y d i f f e r e n t behaviour responses. A l s o , the p h y s i o l o g i c a l age of the f l i e s under study must be known. Responses to v a r i o u s s t i m u l i can be expected to change during the l i f e of a b l a c k f l y as w e l l as w i t h d i f f e r e n t species emerging at d i f f e r e n t p o i n t s i n the season. Simulium , euryadminioulum has been used i n many behaviour tests., but as t h i s species i s the only one known to feed s p e c i f i c a l l y on one host, i t would appear to be a poor choice. I t appears that both v i s u a l and airborne f a c t o r s are i n v o l v e d , to v a r y i n g degrees, i n b l a c k f l y a t t r a c t i o n . Bradbury and Bennett (1974 b)) made one of the most acceptable suggestions so f a r when they c l a s s i f i e d b l a c k f l y responses i n t o h i e r a r c h i c a l - 41 -zones of o r i e n t a t i o n behaviour. T h e i r work should be continued to g r e a t e r depths, and w i t h a wider v a r i e t y of t e s t s p e c i e s . There i s a need f o r e xperimentation to understand what p i t f a l l s e x i s t i n the study of c o l o u r p r e f e r e n c e s . F u r t h e r , an understanding i s needed of the p i t f a l l s t h a t occur i n i n t e r p r e -t i n g f l i g h t a r r e s t a n c e , and d i s t i n g u i s h i n g i t from r e p e l l e n c e i n a r t i f i c i a l o l f a c t o m e t e r c o n d i t i o n s . F i n a l l y , the ignorance of sudoriparous and sebaceous s e c r e t i o n s must be r e c o g n i s e d and r e s e a r c h r e - d i r e c t e d . I t can be concluded t h a t the r o l e of i n d i v i d u a l f a c t o r s i n a t t r a c t a n c y ( c o l o u r , shape, movement, moisture, CC^, sweat, • temperature etc.) w i l l vary g r e a t l y w i t h " o t h e r " c o n d i t i o n s . Response t h r e s h o l d s are r e a d i l y i n f l u e n c e d by any change i n environmental c o n d i t i o n s of e x p e r i m e n t a t i o n . Furthermore, e x t e n s i v e g e n e r a l i z a t i o n s concerning the r e l a t i v e importance of v a r i o u s s t i m u l i are unwarranted u n t i l f u r t h e r work has been done on a d d i t i o n a l b l a c k f l y s p e c i e s . - 42 2. THE SPECIES CONCEPT 2.1 GEOGRAPHICAL DISTRIBUTION B l a c k f l i e s can be found almost anywhere i n the world where s u i t a b l e water courses e x i s t f o r the development of the l a r v a l stage. Even sma l l remote oceanic i s l a n d s such as S t . Helena and Crozet have been c o l o n i z e d by b l a c k f l i e s . On small i s l a n d s where there may be no indigenous mammals, the b l a c k f l y s p e c i e s are i n v a r i a b l y b i r d f e e d e r s of the genus Eusimilium- Mountainous areas, where f a s t - f l o w i n g streams are abundant, are f r e q u e n t l y r i c h e r i n s p e c i e s than the lowlands. A n t h r o p o p h i l o u s s p e c i e s , those which b i t e humans, have not been reco r d e d above 5,000 f e e t (1,530 m), but other s p e c i e s have been found at 15,275 f e e t (4,700 m) i n the C h i l e a n Andes, and up to 14,700 f e e t (4,250 m) on Mt. Kenya (Crosskey 1973). C a r l s s o n suggested i n 1962 t h a t approximately 1,000 s p e c i e s of b l a c k f l i e s had been r e c o g n i s e d throughout the world, and Crosskey (1973) has s i n c e r e p o r t e d over 1,000 s p e c i e s . T h i s number i s l i k e l y to continue to r i s e as p r e v i o u s l y unworked areas of the world are e x p l o r e d . The e v i d e n t disagreements on taxonomic c r i t e r i a f o r d e f i n i n g s p e c i e s has been, and cont i n u e s to be, c o n f u s i n g to the s p e c i e s count. Canada boasts over 100 s p e c i e s of b l a c k f l y (Fredeen 1974) . C a r l s s o n (1962) has r e p o r t e d 36 s p e c i e s and 3 v a r i e t i e s f o r S c a n d i n a v i a . Rubzov (1959-1962) d e s c r i b e d 331 s p e c i e s and 64 v a r i e t i e s f o r the U.S.S.R. In England 35 s p e c i e s of b l a c k f l y are recorded, although o n l y two are known as pests o f man 43 --(Crosskey 1974, p e r s . comm.). Information on the range of i n d i v i d u a l s p e c i e s i s incom-p l e t e , although some d i s t r i b u t i o n maps e x i s t f o r the d i s e a s e v e c t o r Simulium damnosum (Crosskey 1973) . However, i t would be u s e f u l to know the exact range of other important b l a c k f l y s p e c i e s . 2.2 TAXONOMY A l l a spects of b l a c k f l y r e s e a r c h r e q u i r e a f i r m and c o r r e c t i d e n t i f i c a t i o n o f the s p e c i e s i n v o l v e d . Comparatively l i t t l e work has been done on b l a c k f l y taxonomy, p a r t i c u l a r l y i n rec e n t y e a r s , and most r e s e a r c h e r s today r e l y h e a v i l y on the c r i t e r i a e s t a b l i s h e d at the tu r n of the t w e n t i e t h c e n t u r y . However, there i s no gen e r a l agreement among r e s e a r c h e r s today as to which f a m i l y d i v i s i o n s to f o l l o w f o r the Simuliidae. The p o s s i b l e extremes are pres e n t e d by Enderlein(1922) who, on the one hand, r e c o g n i s e d 7 s u b - f a m i l i e s and 50 genera, and Edwards (1915) who, on the other hand, suggested 2 genera and 5 sub-genera. Other authors d i f f e r s t i l l . Smart (1945) suggested 2 s u b - f a m i l i e s and 6 genera; Dyar and Shannon (1927) r e c o g n i s e d 3 genera; and Rubzov (1959-1962) r e c o g n i s e d 2 s u b - f a m i l i e s and 17 genera. As there has been no f i r m acceptance or r e j e c t i o n o f any of these f a m i l y d i v i s i o n s , more recent taxonomic work i s based on one o f the afore-mentioned authors' c r i t e r i a , the c h o i c e being e n t i r e l y t h a t o f the r e s e a r c h e r . T h i s has very o b v i o u s l y l e d to c o n s i d e r a -bl e c o n f u s i o n i n the l i t e r a t u r e . It would appear that even the g e n e r i c c r i t e r i a are s t i l l i n d i s p u t e . For example, i n 1914 M a l l o c h d e s c r i b e d a c e r t a i n - 44 -! . FIGURE 4. A SIMPLIFIED FAMILY TREE OF THE ORDER DIPTERA c C T - J -a N E M A T O C E R A 03 -a -a o 'a •? "S c c o r- o 9 T3 jg -a := r2 •3 _NO CO - 3 CJ r £ _ < O W CO S I I I I I I I I I I I I I 9} o "5 •g a 'C OJ _ -§•1 Pupipara | ^ Larvae uterine Acalyptrata v Calyptrata CYCLORRHAPHA BRACHYCERA Puparium stabilized Venation, antennae reduced Spiracles dorsal or terminal Spiracles at sides • Pti l inum evolved _Squamae enlarged L: Mandibles vertical Head reduced A: Max. palp 1-segroented • Posterior spiracles on plate • Posterior spiracles large L: Distinct head Mandibles sidewise Spiracles equal A: Max. palp 3-segmented Mandibles From: Ross, H.H. (1965). 45 -b l a c k f l y s p e c i e s as Prosimulium pecuarum. Since t h a t date t h i s s p e c i e s has been p l a c e d i n th r e e d i f f e r e n t genera; B r a d l e y (1935) d e s c r i b e d a s p e c i e s as Eusimulium pecuarum', Rempel and Arnason (1947) r e f e r r e d to Simulium pecuarum, and more r e c e n t l y Crosskey (1973) r e f e r s to Cnephia pecuarum. E i t h e r the g e n e r i c c r i t e r i a have never been s a t i s f a c t o r i l y d e f i n e d , or p o s s i b l y the s p e c i e s have been confused i n the p a s t . C e r t a i n l y there are c o n f u s i n g s i m i l a r i t i e s between the d i f f e r e n t s p e c i e s r e c o g n i s e d to date, and v e r y o f t e n taxonomy appears not to be based on w e l l - d e f i n e d and c o n s i s t e n t c r i t e r i a . O c c a s i o n a l l y a s p e c i e s name suddenly appears i n a p i e c e of l i t e r a t u r e , when v i r t u a l l y no mention has been made of i t b e f o r e , and yet i t i s not d e s c r i b e d as a new s p e c i e s . For example, Fredeen (1973) r e f e r s to Simulium defoliarti as a s p e c i e s o u t b r e a k i n g i n B r i t i s h Columbia, and yet there do not appear to be any other r e f e r e n c e s to t h i s s p e c i e s . Even l e s s work i s done on b l a c k f l y l a r v a l taxonomy than on a d u l t , and y e t i t i s u s u a l l y the l a r v a l stage i n v o l v e d i n c o n t r o l programs where c o r r e c t s p e c i e s i d e n t i f i c a t i o n i s e s s e n t i a l . I t i s reasonable to expect t h a t some c l a r i f i c a t i o n o f taxo-nomic r e l a t i o n s h i p s may accrue i n c i d e n t a l l y from the c u r r e n t s t u d i e s being made by c y t o g e n e t i c i s t s on the chromosomal morphology of the s a l i v a r y glands i n b l a c k f l y l a r v a e (Basrur 1959, Basrur and R o t h f e l s 1959, Dunbar 1959, R o t h f e l s and Dunbar 1953). Taxonomic c o n f u s i o n may a r i s e w i t h the d i f f e r e n t s p e c i e s that f r e q u e n t l y f o l l o w one another, o f t e n o v e r l a p p i n g , from a p a r t i c u l a r b r e e d i n g area during the summer months. In c o n c l u s i o n , i t i s obvious t h a t b l a c k f l y taxonomy i s i n - 46 .-somewhat of a s t a t e of c o n f u s i o n . The taxonomic c r i t e r i a suggested need much c l o s e r examination, and the whole system of c l a s s i f i c a t i o n should be agreed upon by the m a j o r i t y of p r e s e n t day workers. An e s s e n t i a l p a r t of any aspect of b l a c k f l y r e s e a r c h i s the c o r r e c t i d e n t i f i c a t i o n of the s p e c i e s concerned, based on w e l l e s t a b l i s h e d and accepted c r i t e r i a such as are l a c k i n g to date. 47 -3. THE ROLE OF BLACKFLIES IN ECOSYSTEMS 3.1 PREDATOR, PARASITE AND COMPETITOR RELATIONSHIPS It i s h i g h l y p e r t i n e n t to know what organisms act as n a t u r a l p a r a s i t e s or p r e d a t o r s of b l a c k f l i e s inasmuch as such, agents might be p r o t e c t e d or enhanced so as to u t i l i z e t h e i r b e n e f i c i a l e f f e c t i n c o n t r o l programs. Furthermore, the r o l e of b l a c k f l i e s i n n a t u r a l ecosystems cannot be f u l l y understood u n t i l a l l p a r a s i t e s , p r e d a t o r s and competitors are r e c o g n i s e d . 3.1.1 Predators N a t u r a l p r e d a t i o n by a wide range of organisms, C a r l s s o n (1962) quotes more than f i f t y p r e d a t o r s p e c i e s , i s known to occur i n b l a c k f l y l a r v a l , pupal and a d u l t stages. However, there i s r e l a t i v e l y l i t t l e l i t e r a t u r e a v a i l a b l e on p r e d a t i o n s t u d i e s , and t h a t which e x i s t s u s u a l l y o n l y r e f e r s to one b l a c k f l y s p e c i e s i n a s p e c i f i c h a b i t a t . It i s o b v i o u s l y d i f f i -c u l t to assess the r e l a t i v e importance of v a r i o u s p r e d a t o r s on a b l a c k f l y p o p u l a t i o n . It appears to be g e n e r a l l y agreed t h a t the primary b l a c k f l y p r e d a t o r s are other i n s e c t s , which u s u a l l y a t t a c k b l a c k f l y l a r v a e . Peterson (1960) found T r i c h o p t e r a (caddis f l y ) l a r v a e to be the most important d e s t r o y e r s o f b l a c k f l y l a r v a e i n Utah. S e v e r a l other authors have recorded c a d d i s - f l y l a r v a e as b l a c k f l y p r e d a t o r s ( C a r l s s o n 1962, Peterson and Davies 1960, Twinn 1939). In C a r l s s o n ' s study of Scandinavian b l a c k f l i e s , the stomach and i n t e s t i n a l content of those animals l i v i n g i n the same h a b i t a t as the b l a c k f l y l a r v a e was c l o s e l y examined. P l e c o p t e r a , 48 T r i c h o p t e r a , Ephemerid and Chironomid l a r v a e had a l l been f e e d i n g to some extent on b l a c k f l y l a r v a e and pupae. Peterson (1960) a l s o observed a q u a t i c b e e t l e (Coleoptera) l a r v a e , Hymenoptera and D i p t e r a s p e c i e s , p r e y i n g on s i m u l i i d s . The Hymenopterans i n v o l v e d were ant s , and although p u b l i s h e d records of such p r e d a t i o n are few, Peterson c o n s i d e r e d t h a t p r e d a t i o n by ants i s more common than had been p r e v i o u s l y suspected. The D i p t e r a n s observed as p r e d a t o r s i n Utah were a d u l t d a n c e - f l i e s (empidids) and a d u l t long-legged f l i e s ( d o l i c h o p o d i d s ) . The d a n c e - f l i e s were observed by Peterson to be f e e d i n g both on a d u l t and l a r v a l s i m u l i i d s . Long-legged f l i e s have been reco r d e d as p r e d a t o r s on l a r v a l s i m u l i i d s (Twinn 1939)', however, Peterson observed o n l y one d o l i c h o p o d i d to prey on an a d u l t b l a c k f l y . D r a g o n f l i e s (Odonata) are known to capture and k i l l a d u l t b l a c k f l i e s . Although there i s very l i t t l e documentation of t h i s (Twinn 1939) , the " p r o t e c t i o n " g i v e n from b i t i n g f l i e s by the predaceous h a b i t s of d r a g o n f l i e s , i s w e l l known by many workers and t r a v e l l e r s out of doors i n the summer months. Twinn r e p o r t e d that "when d r a g o n f l i e s were i n t r o d u c e d i n t o i n f e s t e d t e n t s i n the woods, they would feed upon the mosquitoes and b l a c k f l i e s p resent u n t i l thoroughly gorged." Presumably d r a g o n f l i e s would have to be numerous bef o r e t h e i r f e e d i n g a c t i v i t i e s c o u l d make any impact on a b l a c k f l y p o p u l a t i o n . F i s h are known to be important p r e d a t o r s of b l a c k f l y l a r v a e , yet there i s no d e f i n i t i v e work on the r o l e of b l a c k f l i e s i n f i s h food c h a i n s . Evidence that c e r t a i n f i s h s p e c i e s feed on b l a c k f l y l a r v a e i s u s u a l l y based on stomach content a n a l y s e s , but very few - 49 such analyses have been performed. Cameron (1922) c o n s i d e r e d that the common sucker, Catastomus. aommersonii, i s much more important as a n a t u r a l c o n t r o l f a c t o r i n Saskatchewan than any other p r e d a t o r y s p e c i e s . He s t a t e d t h a t "the contents of the a l i m e n t a r y c a n a l appeared to c o n s i s t of n o t h i n g e l s e but S. simile (= S. arctioum) l a r v a e and pupae, of which the l a r v a e were more abundant. The f i s h were simply gorged w i t h them." Baranov (1937) ( C i t e d Twinn 1939) i n d i c a t e d t h a t i n the Danube, the small sturgeon, Acipenser ruthenis, feeds almost e x c l u s i v e l y on the l a r v a e of Simulium eolumbaozense from March to June, and d e s t r o y s l a r g e numbers of them, about 2,000 have been found i n one small f i s h . Hocking and P i c k e r i n g (1954) , i n s t u d y i n g the bionomics of n o r t h e r n Simuliidae , found b l a c k f l y l a r v a e i n the' stomachs of w h i t e f i s h , but only i n the female f i s h . In Peterson's study o f Utah b l a c k f l i e s (1960), small s c h o o l s of rainbow t r o u t , Salmo gairdnerij were observed f e e d i n g v o r a c i o u s l y on s i m u l i i d l a r v a e a t t a c h e d to l o o s e rocks i n shallow r a p i d s of the study area. C a r l s s o n ' s study of Scandinavian b l a c k f l i e s (1962) i n c l u -ded stomach content analyses of Salmo trutta and Thymallus thymallusj both r e s i d e n t i n b l a c k f l y i n f e s t e d streams. Both s p e c i e s are c o n s i d e r e d to f e e d , to a g r e a t e x t e n t , on b l a c k f l y l a r v a e . C e r t a i n l y , what few o b s e r v a t i o n s have been made, suggest that c e r t a i n f i s h s p e c i e s are important p r e d a t o r s of b l a c k f l y l a r v a e . The q u e s t i o n s t i l l unanswered i s , what degree of depen-dence do the f i s h have on b l a c k f l y l a r v a e as food? Records of b i r d s as p r e d a t o r s of b l a c k f l y l a r v a e are r e l a -t i v e l y few. Hocking and P i c k e r i n g (1954) observed Zonotvichia - 50 -leucophrys, the white - crowned sparrow, f e e d i n g on a d u l t Simulium venustum at a r a t e of 54 f l i e s per f i v e minutes. C a r l s s o n (1962) has recorded the importance of d i p p e r s f e e d i n g on b l a c k f l y l a r v a e , and swallows f e e d i n g on the a d u l t s . A s h o r t study of shore and wading b i r d s p r e y i n g on b l a c k f l y l a r v a e i n O n t a r i o has r e v e a l e d some very i n t e r e s t i n g f i g u r e s (James 1968) . A l l of the b i r d s c o l l e c t e d (2 to 4 i n d i v i d u a l s of each b i r d s p e c i e s feeding) co n t a i n e d Simulium. One m a l l a r d , Anas p. platyrhynchos, was found to have eaten 6050 l a r v a e and pupae, another, 2970. James concluded that b i r d s may be more important r e g u l a t i n g agents f o r b l a c k f l i e s than h i t h e r t o r e a l i z e d . The i n s e c t i v o r o u s p l a n t Pinguiaula vulgaris i s r e p o r t e d to feed on b l a c k f l i e s i n S c a n d i n a v i a ( C a r l s s o n 1962). 3.1.2 P a r a s i t e s The most f r e q u e n t l y recorded p a r a s i t e s of b l a c k f l i e s are Miorosporidia, Nematodes of the genus Mermis, and c e r t a i n f u n g i . The p a r a s i t e s a t t a c k i n the l a r v a l stage, i n v a r i a b l y c a u s i n g m o r t a l i t y . M i c r o s p o r i d i a : No up-to-date keys e x i s t f o r the Mioro-sporidia known to i n f e c t b l a c k f l i e s , but e i g h t e e n s p e c i e s have been recorded f o r North America (Jamnback 1973). I n f e c t e d l a r v a e are e a s i l y r e c o g n i s e d by l a r g e , g l o b u l a r , opaque-white masses, v i s i b l e beneath the c u t i c l e of the abdomen. S t r i c k l a n d (1913) r e p o r t e d v a r i o u s s p e c i e s o f Microsporidia as c a u s i n g from one percent to 80 percent m o r t a l i t y i n s i m u l i i d broods around Boston. Few other f i g u r e s appear to be a v a i l a b l e with regard to the impact of t h i s p a r a s i t e . Twinn (1939) recorded 24 percent as the - 51 h i g h e s t r a t e of l a r v a l i n f e c t i o n around Ottawa, v a r i o u s s p e c i e s being a f f e c t e d . I t i s not c l e a r i n the l i t e r a t u r e whether or not a l l m i c r o s p o r i d i a n i n f e c t i o n s are f a t a l . • Hocking and P i c k e r i n g (1954) r e p o r t e d Protozoan i n f e c t i o n s i n the pupae of Simulium venustum, but t h i s i n f e c t i o n might not have been i n i t i a t e d i n the l a r v a l stage. I can f i n d no r e f e r e n c e to a d u l t b l a c k f l i e s being p a r a s i t i z e d by Microsporidia. More i n f o r m a t i o n i s needed on t h i s h o s t / p a r a s i t e r e l a t i o n s h i p . Mermithids: Mermithids are o b l i g a t e nematode p a r a s i t e s , g e n e r a l l y a s s o c i a t e d w i t h l a r v a l b l a c k f l i e s . Although a d u l t b l a c k f l i e s i n f e c t e d with nematodes of the genus Mermis have been c o l l e c t e d , i t i s u n c e r t a i n whether these r e p r e s e n t i n f e c t i o n s a c q u i r e d l a t e i n the l a r v a l stage of the b l a c k f l y , or d i f f e r e n t s p e c i e s o f Mermis t h a t do not i n h i b i t p u p a t i o n . Advanced i n f e c -t i o n s can be d e t e c t e d r e a d i l y i n the l a r v a , as the p a r a s i t e can be seen l y i n g c o i l e d i n the hemocoele of the semi-transparant b l a c k f l y abdomen. Pupation i s e i t h e r r e t a r d e d or prevented by such i n f e c t i o n s (Jamnback 1973). In North America some b l a c k f l y p o p u l a t i o n s are p a r a s i t i z e d by v a r i o u s genera of mermithids w i t h m o r t a l i t i e s of up to 95 percent (Maser 1973) . Mermithids are p r e s e n t l y being c o n s i d e r e d as b i o l o g i c a l c o n t r o l agents f o r b l a c k -f l i e s ( L a i r d 1972). F i e l d and l a b o r a t o r y s t u d i e s by a team of r e s e a r c h e r s i n Newfoundland are being d i r e c t e d towards d e t a i l e d b i o l o g i c a l s t u d i e s of the mermithids present i n n a t u r a l p o p u l a t i o n s of Canadian b l a c k f l i e s . C e r t a i n l y these n a t u r a l p a r a s i t e s are being s e r i o u s l y c o n s i d e r e d f o r i n t r o d u c t i o n on an enormous s c a l e , with the hope of g a i n i n g some degree of c o n t r o l over b l a c k f l y - 52 p o p u l a t i o n s . Fungi: The fungus Coelomyoidium simulii has been known as a p a r a s i t e of b l a c k f l y l a r v a e s i n c e 1913 ( S t r i c k l a n d ) . I t has been recorded from A f r i c a , Europe, North and South America (Jamnback 197 3). I n f e c t e d l a r v a e are not swollen or d i s t o r t e d , as w i t h m i c r o s p o r i d i a n or mermithid i n f e c t i o n s , but round c y s t s can be seen below the l a r v a l c u t i c l e . S e v e r a l s p e c i e s have been found i n f e c t e d i n New York, but the t o t a l percentage recorded by Weiser, (1964) f o r t h a t area, was o n l y one p e r c e n t . There do not appear to be any other i n d i c a t i o n s of the importance of t h i s fungus i n the l i t e r a t u r e , except t h a t i t i s u s u a l l y , i f not always, f a t a l to the host l a r v a . Beyond these three groups of p a r a s i t e s other organisms have r e c e i v e d very l i t t l e a t t e n t i o n . Reference has been made to l a r v a e o f water mites {Hydrachnoidea) p a r a s i t i z i n g b l a c k f l y pupae and a d u l t s (Peterson I960,- Twinn 1939), but these arthropods are not c o n s i d e r e d of any great importance. 3.1.3 Competitors Although C a r l s s o n (1962) r e p o r t s more than 50 s p e c i e s of b l a c k f l y p r e d a t o r , and the same number of p a r a s i t e s , nowhere i n any of the l i t e r a t u r e can I f i n d r e f e r e n c e to b l a c k f l y c o m p e t i t o r s . There i s one b r i e f r e f e r e n c e to " c o m p e t i t o r s " i n streams emerging and competing w i t h male b l a c k f l i e s on the stream margins, but no i d e n t i f i c a t i o n s are given ( C a r l s s o n 1962) . It seems somewhat l a c k i n g t h at no e c o l o g i c a l study o f b l a c k f l i e s has taken note o f c o m p e t i t o r s . In order to under-stand the f u l l r o l e of b l a c k f l i e s i n ecosystems, p o t e n t i a l 53 competitors must be i d e n t i f i e d . It may be t h a t d i f f e r e n t b l a c k -f l y s p e c i e s compete w i t h i n a c e r t a i n h a b i t a t , a p o s s i b i l i t y which c o u l d be turned to use i f n o n - b i t i n g s p e c i e s c o u l d be i n t r o d u c e d to dominate and e l i m i n a t e s p e c i e s that are s e r i o u s b i t i n g p e s t s . Research i n t o b l a c k f l y competitors i n both l a r v a l and a d u l t stages i s needed. 3.2 THE ROLE AND IMPORTANCE OF BLACKFLY LARVAE AND ADULTS IN  FOOD CHAIN? ; Important reasons may be d e s i g n a t e d f o r a c o n s i d e r a t i o n o f b l a c k f l i e s as consumers and consumed organisms. The l a r v a e are consumers i n streams, and i n t u r n become food c o n s t i t u e n t s i n the d i e t a r y o f f i s h , c e r t a i n predaceous i n s e c t s , and b i r d s . To whatever extent they may be important h a r v e s t e r s o f m i c r o b i o t a , and i n t u r n , important prey f o r f i s h , e i t h e r d i r e c t l y or i n d i r e c t -l y , any programs of c o n t r o l o f these i n s e c t s i n streams must be planned w i t h c a u t i o n . Otherwise, even such forms of combat which do not p o l l u t e f r e s h water systems c o u l d a ct to the detriment of f i s h e r i e s . Furthermore, an e v a l u a t i o n o f the r o l e of v a r i o u s m i c r o b i o t a i n the food, and of the p r e d a t o r s and c o m p e t i t o r s , may pr o v i d e c l u e s to some of the causes of d i f f e r e n c e s i n b l a c k f l y p o p u l a t i o n s at d i f f e r e n t times, p l a c e s and water c o n d i t i o n s . However s l i g h t the f e a s i b i l i t y may appear at the moment, i t i s c o n c e i v a b l e t h a t some manipulations might be imposed on some of the f o r e g o i n g f a c t o r s , f o r the purpose of re d u c i n g b l a c k f l y p o p u l a t i o n s without causing damage to other r e s o u r c e s . C o n c e p t u a l l y , competitors, f o r food and m i c r o h a b i t a t would pro v i d e the best media f o r c o n t r o l , inasmuch as they would s t i l l 54 FIGURE 5. TROPHIC LEVELS IN FOOD CHAINS INVOLVING BLACKFLIES Per la ( P L E C O P T E R A ) Dinocras ( P L E C O P T E R A ) S E C O N D A R Y a T E R T I A R Y C O N S U M E R T R O P H I C L E V E L S Rhyacophila ( TRICHOPTERA ) P R I M A R Y C O N S U M E R T R O P H I C L E V E L P R O D U C E R TROPHIC L E V E L Protonemura ( P L E C O P T E R A ) Ecdyanurus ( E P H E M E R O P T E R A ) L e a f f r a g m e n t s Ulothrix and other g r e e n a l g a e D e t r i t u s Diatoms - A m o r p h o u s v e g e t a b l e m a t t e r + f i n e g r i t + empty a l g a l cells Modified after | j .R.Er ichsen Jones 1949 - 55 -be a v a i l a b l e i n the food c h a i n s . Information on the e c o l o g i c a l r o l e of b l a c k f l i e s i s scan t y , s c a t t e r e d and d i f f i c u l t to t r a c e . Some of the most i n f o r m a t i v e l i t e r a t u r e has been produced by, and addressed t o , f i s h e r i e s b i o l o g i s t s and e c o l o g i s t s o f fresh-water systems. T h i s important aspect o f the s u b j e c t has been l a r g e l y ignored by e n t o m o l o g i s t s . An example o f the p l a c e of b l a c k f l i e s i n food chains i s shown diagramm'atically by Jones (1949) i n the accompanying diagram. 3.2.1 F i s h food chains B l a c k f l y l a r v a e are an important element i n the food c h a i n of many f i s h s p e c i e s . T h i s i s w e l l documented by f i s h - g u t - c o n t e n t s t u d i e s performed on a v a r i e t y of f i s h s p e c i e s i n the past (Baranov 1937; C a r l s s o n 1962; Edwards 1921; Hocking and P i c k e r i n g 1954; M a r l i e r 1952; Mundie 1968). I t i s important to know which f i s h s p e c i e s depend on a food supply o f b l a c k f l y l a r v a e , how great t h i s dependence i s , and whether or not the f i s h can s u r v i v e without a b l a c k f l y p o p u l a t i o n should a c o n t r o l program be s e l e c -t i v e l y aimed at b l a c k f l i e s . B l a c k f l y l a r v a e are u s u a l l y found a t t a c h e d i n areas o f shallow t u r b u l e n t water, where i t would appear t h a t there are few r e s i d e n t f i s h s p e c i e s . However, i t i s not so much the l a r v a e a t t a c h e d to rocks t h a t f a l l prey to f i s h , as the l a r v a e t h a t are d r i f t i n g as p a r t of a general i n v e r t e b r a t e d r i f t downstream. B l a c k f l y l a r v a e are recorded as "abundant i n the d r i f t " (Mundie 1968). In the small stream and r i v e r under Mundie's study, Simulium l a r v a e were the most important item o f food, i n terms of biomass, f o r the r e s i d e n t coho f r y . U s u a l l y " d r i f t i n g " occurs - 56 -at n i g h t when f i s h are not concerned with f e e d i n g , but Simulium l a r v a e are known to d r i f t by day as w e l l as at n i g h t (Waters 1968) . The e f f e c t of d r i f t i n g i s to c a r r y i n v e r t e b r a t e s from an area of t h e i r p r o d u c t i o n , such as t u r b u l e n t shallows f o r b l a c k -f l i e s , to an area s u i t a b l e f o r f i s h consumption, and to a wider assemblage of f i s h s p e c i e s . There i s c o n s i d e r a b l e v a r i a t i o n i n the composition and u t i l i z a t i o n of d r i f t by d i f f e r e n t f i s h s p e c i e s , but i n one t e s t area of the Stamp R i v e r on Vancouver I s l a n d B r i t i s h Columbia, Mundi (1968) found the d r i f t to comprise 14 p e r c e n t (by number) Simulium l a r v a e . Over a 24-hour p e r i o d the d i e t o f cohoe f r y , i n the same t e s t area, comprised 14 percent Simulium l a r v a e . Some f i s h s p e c i e s are known to feed on b l a c k f l y l a r v a e by s c r a p i n g i n d i v i d u a l s o f f the s u b s t r a t e . Varicortinus tanganioae B o u l l e n g e r feeds p r i m a r i l y on Simulium l a r v a e i n Tanganyika, which i t scrapes from stones w i t h i t s sharp-edged mouth. A l l s p e c i e s of t h i s genus are adapted f o r f e e d i n g i n t h i s way, and are a l s o able to ascend v e r y r a p i d streams. M a r l i e r (1952) suggests the i n t r o d u c t i o n of t h i s f i s h i n A f r i c a where l a r g e s i m u l i i d p o p u l a t i o n s are a problem. Although there i s no comprehensive study on the importance of b l a c k f l i e s i n f i s h food c h a i n s , s e v e r a l authors, w h i l e d e a l i n g w i t h more ge n e r a l aspects of b i o l o g y , have made re f e r e n c e to f i s h f e e d i n g . Hocking and P i c k e r i n g (1954) found b l a c k f l y l a r v a e i n the stomachs of female w h i t e f i s h (Covegonus alupeaformis M i t c h e l l ) from the Saskatchewan R i v e r , and i n d i c a t e d that such f i s h may be u s e f u l p r e d a t o r s . Cameron (1922) looked at three common sp e c i e s i n the same r i v e r , the common sucker (Catastomus 57 commersonii), the f l a t - h e a d e d chub (Platybogio gracilis) and the western goldeye (Hyodon chvysopsis). He found remains of b l a c k f l y l a r v a e i n a l l of the suckers examined, but not i n e i t h e r of the other two s p e c i e s . The "browsing" h a b i t , common to s u c k e r s , may e x p l a i n t h i s apparent f e e d i n g d i f f e r e n c e . Baranov (1937) ( C i t e d Twinn 1939) noted t h a t the small sturgeon (Acipensev ruthenis) f e d almost e x c l u s i v e l y on b l a c k f l y l a r v a e i n the Danube; 2,000 l a r v a e were found i n one small t e n - i n c h f i s h . P e t e r s o n (1960) r e p o r t e d a small school of rainbow t r o u t {Salmo gairdnevi Richardson) f e e d i n g v o r a c i o u s l y on s i m u l i i d l a r v a e a t t a c h e d to rocks i n shallow r a p i d s of a stream i n Utah. C a r l s s o n (1962) suggested t h a t the b l a c k f l y l a r v a e are a v a l u a b l e food to f i s h o n l y when they are " d r i f t i n g " i n the o r g a n i c d r i f t , i . e . when streams are broken by many l a k e s . In h i s o p i n i o n d r i f t i n g l a r v a e i n f o r e s t streams f i n d s u i t a b l e s u b s t r a t a r e a d i l y , and are, t h e r e f o r e , not a v a i l a b l e f o r f i s h food, whereas small streams broken by l a k e s p r o v i d e a l a k e h a b i t a t f o r f i s h , and b l a c k f l i e s t h a t d r i f t i n t o such l a k e s become an a v a i l a b l e food source. T h i s i n t e r p r e t a t i o n i s d i s p u t a -b l e , inasmuch as there i s c o n s i d e r a b l e evidence that b l a c k f l i e s do d r i f t i n streams which are not i n t e r r u p t e d by l a k e s , and t h a t they are an important food to f i s h s p e c i e s d u r i n g t h i s d r i f t i n g . C a r l s s o n o b v i o u s l y took d r i f t i n g to mean aiml e s s f l o a t i n g from a r i v e r or stream i n t o a l a k e , whereas b l a c k f l y l a r v a e ,very o f t e n become p a r t of the d r i f t d u r i n g t h e i r process of " d a n g l i n g " on s i l k e n threads i n the c u r r e n t . A l s o , there i s a p e r i o d when b l a c k f l y l a r v a e feed by browsing. C r a i g suggests that 30 percent - 58 -of l a r v a l l i f e i s spent on the move, browse f e e d i n g (pers. comm. 1974). During t h i s f e e d i n g p e r i o d , and d u r i n g movements on s i l k t hreads, b l a c k f l y l a r v a e i n any stream c o u l d become p a r t of the d r i f t , and an important food to the r e s i d e n t f i s h . At present there appears to be no d e f i n i t e answer to the questioned dependence of v a r i o u s f i s h s p e c i e s on b l a c k f l y l a r v a l p o p u l a t i o n s . R e s u l t s i n d i c a t e great v a r i a t i o n i n the composition of i n v e r t e b r a t e d r i f t , and i n the f i s h u t i l i z a t i o n of t h i s food source. B l a c k f l y l a r v a e and pupae appear to p l a y a h i g h l y s i g n i f i c a n t r o l e i n the food c h a i n of v a r i o u s f i s h s p e c i e s , but t h i s r o l e u r g e n t l y needs f u r t h e r d e f i n i t i o n b e f o r e more c o n t r o l attempts are made i n ignorance. 3.2.2 A v i a n food c h a i n s Both a d u l t and l a r v a l b l a c k f l i e s are eaten by c e r t a i n b i r d s p e c i e s , but the importance of t h i s food i n the d i e t of b i r d s i s u n c e r t a i n . O b s e r v a t i o n s on b i r d f e e d i n g suggest t h a t i n d i v i d u a l s consume l a r g e numbers of b l a c k f l i e s at one feed. Hocking and P i c k e r i n g (1954) observed white-crowned sparrows e a t i n g a d u l t b l a c k f l i e s i n n o r t h e r n Manitoba at a r a t e of approximately 54 f l i e s i n f i v e minutes. C a r l s s o n (1962) noted swallows i n S c a n d i n a v i a f l y i n g w i t h open beaks through b l a c k f l y swarms. In f a c t there are probably v e r y many b i r d s p e c i e s t h a t feed on a d u l t b l a c k f l i e s a t some time i n t h e i r l i v e s , but as yet such documen-t a t i o n i s l a c k i n g . An i n t e r e s t i n g study on wading and shore b i r d s (James 1968) around a b l a c k f l y i n f e s t e d stream i n O n t a r i o , r e v e a l e d t r a c e s of b l a c k f l y l a r v a e i n a l l of the d i f f e r e n t b i r d s p e c i e s observed - 59 -f e e d i n g i n the area. In the m a l l a r d (Anas p. platyrhynchos) over 90 percent of the i n s e c t remains i n the g i z z a r d were Simulium l a r v a e , and one i n d i v i d u a l was found to have 6050 l a r v a e and pupae w i t h i n i t s d i g e s t i v e system. In order to understand the complete r o l e of b l a c k f l i e s i n the v a r i o u s ecosystems, a more d e f i n i t e knowledge of the r o l e of a d u l t and l a r v a l b l a c k f l i e s i n a v i a n food chains i s u r g e n t l y needed. Beyond the c a s u a l o b s e r v a t i o n s made so f a r , d e t a i l e d analyses of the gut content of v a r i o u s b i r d s p e c i e s w i l l be necessary. - 60 -4. THE IMPACT OF BLACKFLIES ON THEIR HOSTS 4.1 THE SPECIES INVOLVED The m a j o r i t y of b l a c k f l y s p e c i e s that feed on b l o o d show a d i s t i n c t p r e d i l e c t i o n f o r f e e d i n g e i t h e r on b i r d s ( o r n i t h o p h i l i c s p e c i e s ) , or on mammals (mammalophilic s p e c i e s ) . A l l of the s p e c i e s r e c o r d e d as f e e d i n g on humans ( a n t h r o p o p h i l i c s p e c i e s ) feed on mammals or b i r d s a l s o , and no s p e c i e s i s known t h a t feeds e x c l u s i v e l y on humans. Because of these a p p a r e n t l y " d i s t i n c t " f e e d i n g p r e f e r e n c e s , many assumptions have been made r e g a r d i n g s p e c i e s i d e n t i f i c a t i o n based on host type. These assumptions have l e d to c o n s i d e r a b l e c o n f u s i o n i n s p e c i e s i d e n t i f i c a t i o n . Species known to b i t e humans, such as Simulium damnosum i n A f r i c a , or Simulium decorum, are not known to b i t e humans over t h e i r e n t i r e range. Simulium aureum was r e p o r t e d l y observed f e e d i n g on g o s l i n g s i n 1927 (Davies and Peterson 1956), but l a t e r Twinn (1939) r e - i d e n t i f i e d t h i s s p e c i e s as Simulium venustum. A l a t e r r e-examination r e v e a l e d the f l i e s to be Simulium rugglesi. Because of the o r i g i n a l m i s - i d e n t i f i c a t i o n , other authors have r e f e r r e d to the f e e d i n g of Simulium aureum on ducks and geese, when i n f a c t t h i s h o s t / b l a c k f l y r e l a t i o n s h i p has not been demonstrated. Such p o i n t s of c o n f u s i o n are not uncommon i n the study o f b l a c k f l y s p e c i e s and host r e l a t i o n s . I t should be remembered that the s t a t e d a s s o c i a t i o n s between p a r t i c u l a r b l a c k f l y s p e c i e s and observed h o s t s , are o f t e n based on l o c a l o b s e r v a t i o n s , which t h e r e f o r e do not i n c l u d e a l l of the p o t e n t i a l host s p e c i e s . - 61 Extreme narrowness of hosts (stenophagy) i s r a r e but i s exempli-f i e d by Simulium euryadminioulum and i t s host the common lo o n . 4 . 2 HOST REACTIONS The nature of mechanical wounding by the b i t e s , the chemical i d e n t i t y o f the t o x i c c o n s t i t u e n t s of the f l y s a l i v a , the p h y s i o -l o g i c a l a c t i o n and the c y t o l o g i c a l response o f t i s s u e s at the p o i n t of wounding, and the systemic e f f e c t which i s r e l a y e d to other t i s s u e s o f the body, such as the lungs, are s i g n i f i c a n t f o r v a r i o u s reasons. They p r o v i d e c r i t e r i a f o r d e f i n i n g the k i n d s , i n t e n s i t i e s and d u r a t i o n o f host response, and the ranges o f v a r i a b i l i t y o f these i n r e l a t i o n to d e f i n a b l e i n s e c t s p e c i e s , age o f the f l i e s i n days, n e c t a r meals, and other v a r i a b l e s i n the f l i e s , as w e l l as i n numerous f a c t o r s which d i f f e r and change between and w i t h i n i n d i v i d u a l h o s t s . There i s need f o r a c l e a r e r understanding, f o r example, of the r o l e of p h y s i o l o g i c a l age, p h y s i o l o g i c a l s t a t e , g e n e r a l n u t r i t i o n , and s p e c i f i c n u t r i e n t s or p r e v i o u s exposure o f the host to b i t e s . C l i n i c a l l y i t i s d e s i r a b l e to have d e f i n i t i o n s o f the sequence of dermal and systemic changes which take p l a c e , so t h a t e i t h e r s a t i s f a c t o r y progress may be noted or abnormal trends can be d e t e c t e d f o r s p e c i a l treatment. The c l i n i c a l f e a t u r e s o f b i t e s p r o v i d e the immunologist with c e r t a i n c r i t e r i a by which immunologic r e a c t i o n s may be compared wi t h c o n t r o l s . In the event that they are ha p t e n i c , non-proteinaceous, and n o n - a n t i g e n i c i n themselves, and i n the f u r t h e r event t h a t the host has no mechanisms f o r c o n v e r t i n g such h a p t e n i c substances i n t o a n t i g e n s , then hapten-- 62 -p r o t e i n complexes may be s y n t h e s i s e d or e x t r a c t e d from the i n s e c t (Graham, K. 1975, p e r s . comm.). 4.2.1 C l i n i c a l d e t a i l s of host r e a c t i o n s Human r e a c t i o n s to the b i t e s of b l a c k f l i e s are both p h y s i o l o g i c a l and p s y c h o l o g i c a l , and although the p h y s i o l o g i c a l aspect has r e c e i v e d most a t t e n t i o n i n the p a s t , i t must be emphasized t h a t the p s y c h o l o g i c a l e f f e c t s are e q u a l l y s e r i o u s . Most work on b i t i n g f l i e s and host r e a c t i o n s r e f e r s to mosquitoes, whereas r e l a t i v e l y l i t t l e work has been done on the host r e a c t i o n s to b l a c k f l y b i t e s . However, the c l i n i c a l a s pects of the b i t e , and the secondary c o n d i t i o n of i n f e c t i o n f o l l o w i n g s c r a t c h i n g , have been f a i r l y w e l l d e s c r i b e d i n the l i t e r a t u r e ( F a l l i s 1964, G e o r g e v i t c h 1923, Gudgel and Graver 1954, Hocking 1952, Peterson and Wolfe 1958, Stokes 1914). What i s a p p a r e n t l y l a c k i n g i s a c l e a r u n derstanding of the determinants of acuteness of the r e a c t i o n , and of the nature of the t o x i n s i n v o l v e d . I t i s not known why some people r e a c t more than o t h e r s , or why s u s c e p t i b i l i t y appears to change d u r i n g a season when there i s no evidence of any a n t i g e n i c p r o p e r t y to the b l a c k f l y t o x i n , or of an antibody response i n the host. When the b l a c k f l y b i t e s i t i n j e c t s s a l i v a i n t o the wound i t has made, be f o r e sucking up blood. The s a l i v a i s a l l e g e d to c o n t a i n a n t i c o a g u l a n t s and a g g l u t i n i n s ; the l a t t e r helps to form a s e m i - s o l i d b l o o d mass i n the f l y gut (Yang and Davies 1974). The i n j e c t i o n of s a l i v a i n t o the host v e r y o f t e n causes acute s w e l l i n g and i t c h i n g , which may p e r s i s t f o r s e v e r a l weeks. Furthermore, the r e a c t i o n s may i n v o l v e a c o n d i t i o n known as 63 -" b l a c k f l y f e v e r " , which i s manifest as a headache, swo l l e n -glands, f e v e r and nausea. Such r e a c t i o n s are not uncommon among c h i l d r e n b i t t e n by b l a c k f l i e s i n eastern Canada, and even deaths have been r e p o r t e d (Hocking 1952) . When c a t t l e are b i t t e n by b l a c k f l i e s , deaths are f r e q u e n t l y recorded. W i t h i n an hour of b i t i n g , under severe a t t a c k , the animal's r e s p i r a t i o n becomes deep and r a p i d . In a f a t a l case, r a p i d r e s p i r a t i o n i s f o l l o w e d by s h i v e r i n g , the animal drops to the ground, gasps f o r b r e a t h and d i e s without a s t r u g g l e . Deaths occur r a p i d l y w i t h i n 15 minutes to 2 hours a f t e r the f i r s t o b servable s i g n s . I f r e c o v e r y i s to occur i t w i l l be complete w i t h i n 24-28 hours (Peterson and Wolfe 1958). The a c t u a l cause of death i s not f u l l y understood i n c a t t l e , but post-mortems suggest t h a t the c a u s a l mechanism i n v o l v e s r e a c t i o n to t o x i c • f a c t o r s i n the b l a c k f l y s a l i v a . The t o x i n a p p a r e n t l y induces a process which might be termed pneumohydrorrhoea. A c c o r d i n g l y , one o f the accompaniments to the process i s the f i l l i n g o f the lungs w i t h f l u i d , so that death r e s u l t s i n p a r t from drowning, and not by mechanical choking or i n h a l a t i o n o f the f l i e s as was at one time s p e c u l a t e d . It i s c l e a r t h a t i n d i v i d u a l people d i f f e r markedly i n reac-t i v i t y to b l a c k f l y b i t e s , furthermore t h e i r s u s c e p t i b i l i t y changes d u r i n g a season. I t i s u n c l e a r whether such change i s a t t r i b u t a b l e to p h y s i o l o g i c a l changes i n a person i n the f i e l d , and to a c q u i s i t i o n of p a s s i v e immunity, or to d i f f e r e n c e s i n the t o x i c i t y o f the venom of d i f f e r e n t s p e c i e s of b l a c k f l i e s at d i f f e r e n t times d u r i n g a season. 6 4 The chemical nature of the s a l i v a r y t o x i n s i s unknown, but i t does not appear to be n e c e s s a r i l y a n t i g e n i c . There i s , i n f a c t , no evidence that any form of antibody immunity develops i n response to the b l a c k f l y t o x i n , e i t h e r i n humans or i n l i v e s t o c k . Indeed, on a p r i o r i e v o l u t i o n a r y c o n s i d e r a t i o n s one might reason that advantages go to those b l o o d - s e e k i n g organisms which do not c o n t a i n a n t i g e n i c c o n s t i t u e n t s i n the s a l i v a . I f the t o x i n i s non-proteinaceous i t may be regarded as a h a p t e n i c substance which e x i s t s e i t h e r i n p r e c u r s o r combination, or which might be s u s c e p t i b l e to combination w i t h a p r o t e i n to become an a n t i g e n f o r a hapten. T h i s i s an area o f i n v e s t i g a t i o n w e l l worthy of examination, and one which has not, as y e t , been c o n s i d e r e d . Thus the chemical composition of the s a l i v a r y t o x i n s , and the causes o f the d i f f e r e n t r e a c t i o n s to b l a c k f l y b i t e s , as w e l l as the causes of d i f f e r e n c e s i n i n c i d e n c e o f a t t a c k , m e r i t s p e c i a l i n v e s t i g a t i o n i f host r e a c t i o n s are to be understood and manipu-l a t e d f o r the needs of p r o t e c t i o n . 4.3 DISEASE TRANSMISSION '; • B l a c k f l i e s are i n s e c t s of p a r t i c u l a r medical and v e t e r i n a r y importance not onl y because they h a r a s s , t o x i f y , d e b i l i t a t e and k i l l t h e i r h osts by t h e i r a t t a c k sequences, but a l s o because c e r t a i n s p e c i e s t r a n s m i t v a r i o u s pathogenic organisms to humans, mice, r a b b i t s , c a t t l e and b i r d s . The l i s t o f pathogens p r e s e n t l y a s s o c i a t e d w i t h s i m u l i i d v e c t o r s i n c l u d e s v i r u s e s a f f l i c t i n g t u r -keys, mice and r a b b i t s , b l o o d - i n h a b i t i n g protozoan p a r a s i t i z e s of the genus Leucocytozoon Ziemann among b i r d s , and s k i n i n h a b i t i n g f i l a r i a l nematodes of the genus Onchocerca D i e s i n g i n mammals, - 65 -i n c l u d i n g humans. 4.3.1 Human o n c h o c e r c i a s i s Although b l a c k f l i e s are not known to t r a n s m i t any human di s e a s e s i n North America, c e r t a i n s p e c i e s i n t r o p i c a l A f r i c a and i n p a r t s of the t r o p i c a l Americas t r a n s m i t the nematode Onchocerca volvulus to humans, prolonged i n f e c t i o n w i t h which causes the b l i n d i n g d i s e a s e o n c h o c e r c i a s i s ( " r i v e r b l i n d n e s s " ) . The two c h i e f v e c t o r s i n A f r i c a are Simulium neavei and Simulium damnosum. In the t r o p i c a l Americas Simulium ochvaceums Simulium metallicum and Simulium woodi, as w e l l as the two forementioned s p e c i e s are i m p l i c a t e d . As v e c t o r s of t h i s agent of d i s e a s e , b l a c k f l i e s rank amongst the most troublesome and p a i n - c a u s i n g i n s e c t p e s t s o f humans and animals i n many p a r t s o f the world. I t i s noteworthy that o n c h o c e r c i a s i s i s not r e c o r d e d over the e n t i r e ranges of the v e c t o r b l a c k f l y s p e c i e s , e i t h e r i n t r o p i c a l A f r i c a or the t r o p i c a l Americas. The reasons f o r the p r e s e n t p a t t e r n of d i s e a s e d i s t r i b u t i o n are u n c e r t a i n and r e q u i r e f u r t h e r study. " O n c h o c e r c i a s i s i n man i s c h a r a c t e r i s e d by i n t e n s e i t c h i n g , l i c h e n i f i c a t i o n and f i s s u r i n g of the s k i n , the occurrence o f subcutaneous nodules where the t i s s u e s are t h i n over the bones, and, i n the worst cases, of i r r e v e r s i b l e b l i n d n e s s " (Crosskey 1973) . A d u l t worms are to be found i n the human host i n small nodules immediately below the s k i n s u r f a c e , each nodule c o n t a i n i n g one or s e v e r a l male and female worms. In t h i s stage the male worms are 2-4 cm long and the female 35-70 cm. Each f e r t i l i z e d - 66 -female worm produces thousands of t i n y m i c r o f i l a r i a e t h a t move slow l y around the host under the s k i n , but a p p a r e n t l y do not enter the blood stream. The p r e c i s e route of these m i c r o f i l a r i a e i s not c l e a r l y s t a t e d . I t i s known that dead p a r a s i t e s , p a r t i c u -l a r l y m i c r o f i l a r i a e can cause most of the damage to the s k i n and eyes, as a r e s u l t o f damage and r e a c t i o n f o l l o w i n g a b s o r p t i o n of t h e i r c o n t a i n e d substances (W.H.O. 1966). When an i n f e c t e d person i s b i t t e n by a p o t e n t i a l v e c t o r b l a c k f l y , m i c r o f i l a r i a e are taken up d u r i n g the blood meal. As many as 200 may be i n g e s t e d at one fe e d , but o f t e n not more than one or two s u r v i v e to develop i n the i n t e r m e d i a t e host. The. m i c r o f i l a r i a e migrate to the thorax of the b l a c k f l y , where development and m a t u r i t y occur i n about 7 days. Mature i n d i v i d u -t a l s e nter the s a l i v a r y glands, and so are i n j e c t e d , w i t h the b l a c k f l y s a l i v a , i n t o a host d u r i n g normal b l o o d - f e e d i n g a c t i v i -t i e s (Symes et al. 1962). U n l i k e m a l a r i a l p a r a s i t e s , the micro-f i l a r i a e do not m u l t i p l y i n the i n s e c t host. In f a c t r e l a t i v e l y few s u r v i v e to enter the human body, and even those may not pro-duce d i s e a s e . The c y c l e i s completed when i n j e c t e d m i c r o f i l a r i a e mature i n the host and a d u l t worms aggregate to nodules where r e p r o d u c t i o n occurs and d i s e a s e s i g n s appear. The movement of m i c r o f i l a r i a e w i t h i n the human host body i s ina d e q u a t e l y d e s c r i b e d i n the l i t e r a t u r e , although a p p a r e n t l y they do not enter the blood. T h i s aspect warrants a f u l l e r understand-i n g p a r t i c u l a r l y i f c e r t a i n forms of therapy are to be e f f e c t i v e . Over 30 m i l l i o n people i n t r o p i c a l A f r i c a and the t r o p i c a l Americas are known to be s u f f e r i n g the e f f e c t s of o n c h o c e r c i a s i s , 67 and many i n d i v i d u a l s are p a r t i a l l y or f u l l y b l i n d e d as a r e s u l t . As t h i s i s mainly a r u r a l d i s e a s e , the b l i n d e d v i c t i m s , unable to work, become a heavy burden on t h e i r f a m i l i e s , and the conse-quent economic ha r d s h i p s are severe. T h i s has happened to such an extent that l a r g e f e r t i l e and p o t e n t i a l l y p r o d u c t i v e areas, i n c l u d i n g one t e n t h of the t o t a l area of the savanna r e g i o n s o f West A f r i c a , now l i e abandoned. 4.3.2 Bovine o n c h o c e r c i a s i s In c e r t a i n temperate and t r o p i c a l areas of the world c a t t l e s u f f e r the e f f e c t s of i n f e c t i o n w i t h f i l a r i a l worms of the genus Onchocerca. However, co m p a r a t i v e l y l r t t l e documentation e x i s t s of e i t h e r the outbreaks of t h i s d i s e a s e , or of the e f f e c t s on the c a t t l e h o s t s . Onchocerca gutturosa Neumann i s known to be t r a n s m i t t e d by the b l a c k f l y Simulium ornatum i n England (Crosskey 1973) . E i c h l e r and Nelson (1971) r e p o r t the occurrence of the p a r a s i t e i n Europe, A s i a , North and South America, A u t r a l i a , and A f r i c a . In B e r k s h i r e and H e r t f o r d s h i r e , England, more than 50 p e r c e n t of the c a t t l e examined i n a b a t t o i r s , d u r i n g 1964-1969, w e r e f i n f e c t e d with t h i s p a r a s i t e , although v e t e r i n a r i a n s and meat i n s p e c t o r s were t o t a l l y unaware of the p a r a s i t e s ' presence. Steward (1937) suggested c o n s i d e r a b l y more concern e x i s t s over the d i s e a s e i n A u s t r a l i a , as "worm nodules" due to Onchocerca gibsoni C l e l a n d and Johnson, were estimated to be causing l o s s e s o f J § 5 0 0 , 0 0 0 per annum to Queensland alone. The c a r r i e r i n A u s t r a l i a i s unknown. - 68 -In the U.S.S.R. Gnedina (1959) ( C i t e d E i c h l e r and Nelson 1971) has claimed t h a t i n j u r i e s to the s k i n , caused by i n f e c t i o n s of Onchocerca gutturosa i n c a t t l e , are r e s p o n s i b l e f o r a s i g n i f i -cant p r o p o r t i o n of the l o s s e s to the l e a t h e r i n d u s t r y . In Japan, Nimmi and Kuono (1954) ( C i t e d E i c h l e r and Nelson 1971) found that 90 p e r c e n t of the c a t t l e i n f e c t e d w i t h the m i c r o f i l a r i a e of 0. gutturosa had s i g n s of inflammatory l e s i o n s c o n c e i v a b l y , other s k i n d i s o r d e r s might be a t t r i b u t a b l e to t h i s p a r a s i t e . I t appears t h a t 0. gutturosa has not been i m p l i c a t e d i n human a f f l i c t i o n s , e i t h e r d i r e c t l y or through meat consumption, although i t i s c l o s e l y r e l a t e d to the worm Onchocerca volvulus p r e v i o u s l y d e s c r i b e d . Although i n f e c t i o n s w i t h Onchocerca gutturosa do not appear to be i m p l i c a t e d w i t h the i l l - h e a l t h of c a t t l e , i t i s obvious t h a t no s u b s t a n t i a l study has ever been made of t h i s h o s t / p a r a s i t e r e l a t i o n s h i p . 4.3.3 L e u c o c y t o z o o n i a s i s of b i r d s Of the many b l a c k f l y s p e c i e s t h a t are p e s t s to b i r d s , some are v e c t o r s of a f a t a l m a l a r i a - l i k e d i s e a s e known as " l e u c o c y t o -z o o n i a s i s " . T h i s d i s e a s e i s p r e v a l e n t i n a wide v a r i e t y of a v i a n h o s t s , p a r t i c u l a r l y waterfowl, i n the North American c o n t i n e n t , as w e l l as o t h e r p a r t s of the world. S e v e r a l s p e c i e s of haematogenous p r o t o z o a of the genus Leucocytozoon are i n v o l v e d i n t h i s d i s e a s e , although i t i s b e l i e v e d that each s p e c i e s of Leucocytozoon p a r a s i t e s o n l y one f a m i l y of b i r d s (Crosskey 1973). The range of hosts i n c l u d e s 69 -r o b i n s , grouse, t u r k e y s , and a wide v a r i e t y of waterfowl; some sp e c i e s of s i m u l i i d have been i m p l i c a t e d with more than one s p e c i e s o f Leucooytozoon. In North America Leucooytozoon smithi, t r a n s m i t t e d by Simulium mevidionale and Simulium jenningsi, i s r e s p o n s i b l e f o r c o n s i d e r a b l e l o s s e s to the turkey i n d u s t r y , and ranks as the most d e s t r u c t i v e Leucooytozoon of domestic b i r d s . In the l a t e r 1950's, l e u c o c y t o z o o n i a s i s caused the f a i l u r e of f e d e r a l e f f o r t s to e s t a b l i s h p i l g r i m geese i n Ungava Bay. The geese were shipped from Montreal i n an attempt to e s t a b l i s h food r e s e r v e s f o r n a t i v e Eskimos. However, the non-immune gos-l i n g s proved v u l n e r a b l e to a Leucooytozoon i n f e c t i o n , and a l l attempts at e s t a b l i s h i n g the p o p u l a t i o n f a i l e d . The e f f e c t s o f Leucooytozoon i n f e c t i o n s upon b i r d s i n n a t u r e range from pathogenic to benign, and yet they remain i n a d e q u a t e l y understood. T h i s c o n d i t i o n of ignorance s u r e l y m e r i t s a t t e n t i o n . To quote L a i r d (1972), " L e u c o c y t o z o o n i a s i s causes a great d e a l more s i c k n e s s and death among b i r d s than p e r s i s t e n t s y n t h e t i c p e s t i c i d e s have done, or are ever l i k e l y to do, however r a s h l y the p e s t i c i d e s have been used i n the p a s t " . 4.3.4 Other d i s e a s e s Although there appears to be no evidence at p r e s e n t to i n d i c a t e t h a t s i m u l i i d s are i n v o l v e d i n the t r a n s m i s s i o n of v i r u s e s to man, experimental v i r u s t r a n s m i s s i o n to mice has r e c e n t l y been demonstrated ( A u s t i n 1967) . Austvosimulium ungulatum was used as the experimental t r a n s m i t t i n g agent. V i r u s e s have a l s o been i s o l a t e d from some o r n i t h o p h i l i c b l a c k f l i e s , f o r 70 -example, e a s t e r n e n c e p h a l i t i s (E.E.V.) has been i s o l a t e d from Simulium meridionale exposed to brooder house turkeys (Anderson et al. 1961). Simulium melatum i s r e p u t e d l y i n v o l v e d i n the t r a n s m i s s i o n of myxomatosis v i r u s among r a b b i t s i n A u s t r a l i a (Mykytowycz 1957). The l i s t of pathogens t r a n s m i t t e d by b l a c k f l i e s has yet to be completed. So f a r i t i n c l u d e s 3 nematode genera, 3 protozoan genera and a few i n c o m p l e t e l y i d e n t i f i e d v i r u s e s . As b l a c k f l y r e s e a r c h s l o w l y advances around the world, and as t r a n s m i s s i o n r e s e a r c h p r o g r e s s e s , i t would seem l i k e l y t h a t t h i s l i s t of pathogens w i l l expand w i t h i n and beyond the p r e s e n t l y d e s c r i b e d genera. - 71 5. THE IMPACT OF BLACKFLIES ON NATURAL RESOURCE USE AND MANAGEMENT B l a c k f l i e s impose t h e i r impact on many aspects o f n a t u r a l r e source use and management, p a r t i c u l a r l y f o r e s t r e s o u r c e s . The mere presence o f these f l i e s has proved an o b s t a c l e to the e f f e c t i v e development of many areas, p a r t i c u l a r l y the n o r t h e r n r e g i o n s , at a time when p r e s s u r e s are being e x e r t e d f o r g r e a t e r access and development. B l a c k f l i e s are i m p l i c a t e d as having been a b a r r i e r to the e x p l o r a t i o n and economic development of the n o r t h s i n c e the e a r l i e s t phases of European c o n t a c t ( L a i r d 1972). A f u l l e v a l u a t i o n of the d i v e r s e impacts o f b l a c k f l i e s i s u r g e n t l y needed. As these f l i e s are a c t i v e out of doors by day, the g r e a t e s t impact i s f e l t w i t h i n the f o r e s t i n d u s t r y , t o u r i s t i n d u s t r y , b u i l d i n g , mining, and "farming e n t e r p r i s e s . B l a c k f l i e s impair the use and value o f f o r e s t r e c r e a t i o n a l areas by harassment of people, as w e l l as of horses used f o r packing or r i d i n g . They impair the p r o d u c t i v i t y o f f o r e s t w i l d l i f e and the waterfowl a s s o c i a t e d w i t h lakes and r i v e r s . They impair the h e a l t h and e f f i c i e n c y of f o r e s t workers, and impede the process of w i l l i n g labour f o r c e s . B l a c k f l i e s a l s o impair c a t t l e p r o d u c t i v i t y w i t h i n the f o r e s t e d range and on many areas o f open range. The impact of b l a c k f l i e s on n a t u r a l r e s o u r c e s may i n v o l v e f u r t h e r environmental problems when a c t i o n s are taken, under p u b l i c or i n d u s t r i a l p r e s s u r e , to a l l e v i a t e the b l a c k f l y problem. The haphazard use o f i n s e c t i c i d e s , e s p e c i a l l y when i n t r o d u c e d d i r e c t l y and d e l i b e r a t e l y i n t o r i v e r s , i n t r o d u c e s r i s k s to - 72 a s s o c i a t e d r e s o u r c e and environmental v a l u e s , such as, the domestic water s u p p l i e s may become p o l l u t e d , and f i s h e r i e s and w i l d l i f e may s u f f e r . Damage to h i g h e r organisms, may accrue i n d i r e c t l y from d e s t r u c t i o n of b l a c k f l y l a r v a e themselves and other a q u a t i c forms which are i n v o l v e d d i r e c t l y or i n d i r e c t l y i n food chains f o r f i s h and h i g h e r forms. Damage might r e s u l t a l s o from the d i r e c t i n j u r i e s of p e s t i c i d e s to the h i g h e r forms of l i f e , and i f c h e m i c a l l y - s t a b l e , f a t - s o l u b l e p e s t i c i d e s are used, they may e n t e r food chains and become p r o g r e s s i v e l y c o n c e n t r a t e d and i n c r e a s i n g l y dangerous i n s u c c e s s i v e consumer organisms, and r e l a y e d from p l a c e to p l a c e . 5.1 THE EFFECT OF BLACKFLIES ON LABOUR FORCE EFFICIENCY AND GROUP MORALE : . " A t t r a c t i n g and m a i n t a i n i n g a s t a b l e labour f o r c e f o r any outdoor work can be s e r i o u s l y impeded by the a c t i v i t i e s of blood-sucking f l i e s . The mere knowledge that b l a c k f l i e s are p r e s e n t may be s u f f i c i e n t to d i s c o u r a g e many workers. As b l a c k f l i e s are a c t i v e by day, and as they can occur throughout the summer months, i t i s v i r t u a l l y i m p o s s i b l e to be u n a f f e c t e d by t h e i r presence and a c t i v i t i e s . Most people s u f f e r more s e v e r e l y from b l a c k f l y b i t e s than from mosquito b i t e s , and the e f f e c t s can be both p h y s i o l o g i c a l and p s y c h o l o g i c a l . B l a c k f l i e s not o n l y a t t a c k exposed areas of the body, but e n t e r any openings there may'be i n c l o t h i n g , such as s l e e v e s , pant c u f f s , s h i r t c o l l a r s or other areas which are not t i g h t l y f i t t e d a g a i n s t the body. The f l i e s then work t h e i r way beneath the c l o t h i n g , and b i t e i n areas where the c l o t h i n g -73 -comes i n t o f i r m c o n t a c t with the body. C l o t h i n g which i s made to exclude b l a c k f l i e s becomes uncomfortably hot, and i f kept to minimum weight, i s i n some cases p e n e t r a b l e by mosquitoes. B l a c k f l i e s are a v i d f e e d e r s and are not r e a d i l y d i s l o d g e d once s e t t l e d to feed. The constant manual removal, necessary i n heavy b l a c k f l y a t t a c k s , i s o b v i o u s l y extremely d i s t u r b i n g and e n e r v a t i n g to the v i c t i m . A f t e r a s h o r t p e r i o d of exposure to b l a c k f l i e s the mere presence of these f l i e s , whether engaged i n f e e d i n g or not, i s s u f f i c i e n t to evoke an i n s t i n c t i v e removal r e a c t i o n , p s y c h o l o g i c a l l y not i n d u c i v e to an e f f i c i e n t work s t a t e . I n d i v i d u a l e f f i c i e n c y , and even more so group morale, i s d r a s t i c a l l y lowered by the p s y c h o l o g i c a l and p h y s i o l o g i c a l e f f e c t s of the presence and a c t i v i t i e s of b l a c k f l i e s . Hocking (1952) suggested t h a t i n d i v i d u a l s may become i n e f f e c t i v e f a r sooner from the p s y c h o l o g i c a l e f f e c t s of b l a c k f l i e s than from d i r e c t p h y s i o l o g i c a l causes. The c o n t i n u a l l y a c c e l e r a t e d and i n c r e a s i n g l y i n e f f e c t i v e removal r e a c t i o n s , can r a p i d l y reduce a s u s c e p t i b l e person to an i n e f f i c i e n t emotional s t a t e . The a t t r a c t i v e n e s s and comfort of f i e l d working c o n d i t i o n s are h i g h l y s i g n i f i c a n t f a c t o r s i n f o r e s t l a b o u r r e c r u i t m e n t , p a r t i c u l a r l y w i t h the g e n e r a l growth and development of our p r e s e n t day economy. B l a c k f l i e s , and other haematophagous D i p t e r a , are regarded as one of the major c a u s a l f a c t o r s of the high l a b o u r turnover i n pulpwood c u t t i n g camps du r i n g the summer months (West 1958). T h i s problem i s i n t e n s i f i e d by the t r e n d towards g r e a t e r summer a c t i v i t y i n the woods d u r i n g the months when the f l i e s are a c t i v e . West records that improved morale and g r e a t e r e f f i c i e n c y r e s u l t 74 from a r e d u c t i o n of b i t i n g f l y a c t i v i t y . Long-term management pl a n s are s e r i o u s l y upset when b l a c k -f l i e s d i s t u r b the work f o r c e . It i s not uncommon f o r work to stop a l t o g e t h e r on p a r t i c u l a r l y bad f l y days. For example, i n the s p r i n g of 1974 near Squamish, i n south-western B r i t i s h Columbia, b l a c k f l i e s were s u f f i c i e n t l y troublesome to cause the c o n t r a c t e d f o r e s t t r e e p l a n t e r s to suspend work u n t i l they c o u l d be p r o t e c t e d by head nets and v e i l s , which impeded the p l a n t i n g o p e r a t i o n s (Wyeth, M. 1974 p e r s . comm.). 5.2 THE IMPACT OF BLACKFLIES ON RECREATIONAL ACTIVITIES The r a p i d l y i n c r e a s i n g development of outdoor r e c r e a t i o n as a s e r v i c e d e r i v a b l e from f o r e s t areas b r i n g s with i t the need and demand f o r i n c r e a s e d a t t e n t i o n to p u b l i c needs and comforts. As other a m enities improve, the f l y problem w i l l become p r o p o r t i o n a t e l y more c r i t i c a l f o r the l e s s s t o i c i n d i v i d u a l s . B l a c k f l i e s are so abundant i n many p l a c e s d u r i n g the summer months, and t h e i r a c t i v i t i e s so h a r a s s i n g , that a person may be b i t t e n dozens of times w i t h i n minutes of l e a v i n g the p r o t e c t i o n of a v e h i c l e or other s h e l t e r . Even a very low b i t i n g and annoyance r a t e can d iscourage r e c r e a t i o n e r s from v i s i t i n g o t h e r -wise a t t r a c t i v e areas. I n d i v i d u a l r e a c t i o n s to b l a c k f l y b i t e s vary q u i t e c o n s i d e r a b l y and i t i s not understood why t h i s i s so. Some people may s u f f e r f e v e r , nausea and headache, as w e l l as p a i n and i t c h i n g at the p o i n t s of i n d i v i d u a l b i t e s . The s c e n i c t u r b u l e n t streams i n f o r e s t e d areas, where mosquitoes as l e s s l i k e l y to be s e r i o u s , are most l i k e l y to - 75 -s u f f e r from b l a c k f l i e s which breed i n such areas. Although very l i t t l e documentation e x i s t s on the impact o f b l a c k f l i e s on r e c r e a t i o n a l a c t i v i t i e s , they are r e c o g n i s e d as having a d e l e -t e r i o u s economic e f f e c t on the t o u r i s t i n d u s t r y (Crosskey 1973). At Mont A p i c a , Quebec, b l a c k f l i e s were r e p o r t e d l y the most formidable nuisance f o r R.C.A.F. personnel i n the l a t e f i f t i e s , to the extent t h a t a l l scheduled outdoor events had to be can-c e l l e d due to the nuisance caused by these f l i e s (Snider 1958). I t was u t t e r l y i m p o s s i b l e to even s i t out of doors d u r i n g the f l y season. 5.3 THE IMPACT OF BLACKFLIES ON FOREST RANGE MANAGEMENT Va r i o u s s p e c i e s o f b l a c k f l i e s , b r e e d i n g i n l a r g e r i v e r s and f a s t - r u n n i n g streams, are i n v a r i a b l y a s s o c i a t e d w i t h g r a s s l a n d / f o r e s t ecotones, and f r e q u e n t l y emerge i n great numbers at a time of year c o i n c i d i n g with the h e r d i n g o f c a t t l e onto summer ranges. Mass a t t a c k s on c a t t l e by b l o o d - t h i r s t y b l a c k f l i e s are a f a i r l y r e g u l a r event i n many areas such as the Canadian p r a i r i e s , where farmers experience c o n s i d e r a b l e l o s s e s . The most n o t o r i o u s s p e c i e s of b l a c k f l y a t t a c k i n g c a t t l e i s the Goloubatz f l y Simulium aolumbasohensis of middle and southern Europe. In the summer of 1923, Romania s u f f e r e d two immense a t t a c k s i n which 16,474 domestic animals were k i l l e d ( C i u r e a and D i n u f l e s c u 1924) . In Canada, the b l a c k f l y Simulium arotiaum has been r e s p o n s i -b l e f o r c o n s i d e r a b l e l i v e s t o c k l o s s e s . Outbreaks of t h i s f l y were recorded d u r i n g 1917, 1918 and 1922 (Cameron 1918, 1922). 76 Only poor r e c o r d s were kept over the next t h i r t y y e a r s , u n t i l the d e v a s t a t i n g outbreaks of 1944 ( M i l l a r and Rempel 1944) . A s e r i o u s b l a c k f l y outbreak was recorded f o r 1946 i n Saskatchewan. In t h i s outbreak f l i e s were borne f o r d i s t a n c e s of 100 m i l e s (170 Km) from t h e i r b r e e d i n g s i t e , and a very l a r g e l o c a l area was i n v o l v e d , w i t h c o n s i d e r a b l e c a t t l e l o s s e s r e s u l t i n g . C l o s e l y r e l a t e d to Simulium aroticum i s the s p e c i e s Simulium def oliavti, which i s found i n c e r t a i n intermontane v a l l e y s of B r i t i s h Columbia (Fredeen 1973) . A c c o r d i n g to Fredeen, S. defoliarti r a r e l y k i l l s animals, but outbreaks can be prolonged s u f f i c i e n t l y to cause a d e c l i n e i n p r o d u c t i v i t y o f both beef and d a i r y c a t t l e . C u r t i s (1954) r e p o r t e d an outbreak of b l a c k f l i e s i n . t h e C h e r y v i l l e d i s t r i c t of B r i t i s h Columbia, but i t i s not c l e a r whether the s p e c i e s i n v o l v e d was a c t u a l l y S. aroticum or a s p e c i e s s i m i l a r to i t . In t h i s outbreak the area a f f e c t e d was only s m a l l , but the s e v e r i t y o f l o s s e s i n weight of c a t t l e , a t t r i b u t a b l e to t h i s p e s t , were c o n s i d e r a b l e . Some ranchers even doubted t h e i r a b i l i t y to remain i n bus i n e s s u n l e s s r e l i e f i s to be o b t a i n e d . A l a s s o f $24,160 was c a l c u l a t e d on beef c a t t l e alone. The c a t t l e t h a t s u f f e r most i n a b l a c k f l y outbreak are the mature i n d i v i d u a l s , the dense h a i r y c o v e r i n g of c a l v e s a p p a r e n t l y o f f e r i n g some p r o t e c t i o n . B i t i n g i s u s u a l l y c o n c e n t r a t e d i n areas where the h a i r i s l e a s t dense, such as the udder of cows and scrotum of b u l l s . T h i s leads to obvious problems when udders become inf l a m e d and c a l v e s are unable to feed f r e e l y . Furthermore, severe inflammation ..of - 77 -the penis sheath i n b u l l s can cause temporary impotence, and consequent displacement of mating and c a l v i n g to an u n p r o p i t i o u s season f o r development and s u r v i v a l . B u l l s are e s p e c i a l l y sus-c e p t i b l e i f they are newly r e l e a s e d onto the range d u r i n g an outbreak p e r i o d . The a l t e r n a t i v e to r e l e a s i n g b u l l s i n the f i e l d d u r i n g the b l a c k f l y season i s to p r o v i d e s t a b l i n g or other s h e l t e r . However, the obvious disadvantage to t h i s i s the expense and inconvenience to ranchers i n p r o v i d i n g the n e c e s s a r y food and a t t e n t i o n . The constant harassment of a b l a c k f l y swarm around c a t t l e w i l l s e r i o u s l y d i s r u p t the g r a z i n g a c t i v i t i e s , and both m i l k and weight l o s s e s are f r e q u e n t l y a s s o c i a t e d w i t h outbreaks o f these f l i e s . The r e a c t i o n to b l a c k f l y b i t e s i s u s u a l l y r a p i d , and w i t h i n an hour of b i t i n g oedematous s w e l l i n g s may be n o t i c e a b l e (Fredeen 1973). Under a severe a t t a c k the animals r e s p i r a t i o n becomes r a p i d and deep, and i n f a t a l cases, t h i s c o n d i t i o n i s f o l l o w e d by s h i v e r i n g , the animal drops to the ground, gasps f o r b r e a t h , and d i e s without a s t r u g g l e . Deaths occur r a p i d l y - w i t h i n f i f t e e n minutes to two hours a f t e r the f i r s t o b servable s i g n s . I f r e c o v e r y i s to occur i t i s u s u a l l y complete w i t h i n 24-48 hours (Peterson and Wolfe 1958). The a c t u a l cause of death i s not f u l l y understood, but post-mortems suggest that the t o x i c a c t i o n of the i n s e c t ' s s a l i v a i s the c a u s a l agent. In e a r l i e r days the i d e a of mechanical s u f f o c a t i o n , o c c a s i o n e d through the i n h a l a t i o n of l a r g e numbers of f l i e s , w i t h a consequent o b s t r u c -t i o n of a i r - p a s s a g e s , was w i d e l y h e l d by laymen. However, p o s t -mortems have r u l e d out t h i s assumption, and death appears to be - 78 caused by an i n c r e a s e i n p e r m e a b i l i t y of the c a p i l l a r i e s , with a consequent great l o s s of f l u i d from the c i r c u l a t o r y system i n t o the t i s s u e s spaces and body c a v i t i e s (Jamnback 1973) . I n t e r n a l organs, body c a v i t i e s and t i s s u e spaces show c o n s i d e r a b l e i m b i b i -t i o n of a c l e a r serous f l u i d , and of i n t e r n a l haemorrhages. As most c a t t l e that d i e as a r e s u l t of b l a c k f l i e s are mature i n d i v i d u a l s , the f i n a n c i a l l o s s to ranchers can be g r e a t . A l s o , the i n t e r r u p t i o n of g r a z i n g a c t i v i t i e s , and consequent weight l o s s e s , means reduced r e t u r n s f o r the ranchers when o r d i n a r i l y c a t t l e might g a i n two pounds (1 kg) a day, i n summer months, without f l y harassment. There remains a need f o r more p r e c i s e m o n i t o r i n g of i n f o r -mation on occurrences of mass a t t a c k s of b l a c k f l i e s . Rempel and Arnason (1947) note that b l a c k f l i e s a t t a c k p a r t i c u l a r l y under the l i g h t shade of t r e e s , i . e . i n f o r e s t range s i t u a t i o n s . T h i s i n t e r p r e t a t i o n appears to be somewhat i n c o n s i s t e n t w i t h the evidence that day-time s h a d e - p r o v i d i n g s h e l t e r s p r o v i d e p r o t e c t i o n from a t t a c k s . However, no study of b i t i n g h a b i t a t p r e f e r e n c e has been made f o r b l a c k f l i e s and c a t t l e . The p r e c i s e c l i m a t i c c o n d i t i o n s p r i o r to and d u r i n g i n f e s t a t i o n s should be recorded i f the development of damaging outbreaks i s to be understood. In f a c t , a l l of the events a s s o c i a t e d w i t h the development of out-breaks need documentation, so t h a t e v e n t u a l l y i t should be p o s s i -b l e to p r e d i c t the time and s e v e r i t y of each impending a t t a c k . Such i n f o r m a t i o n would a l s o serve to r e l i e v e the great element of suspense that ranchers face each year. A l s o , the i n f o r m a t i o n c o u l d be i n c o r p o r a t e d i n t o the p l a n n i n g of l i v e s t o c k management and l a r v i c i d i n g programs. - 79 -6. PRINCIPLES, PRACTICES AND PROBLEMS IN CONTROL OF BLACKFLIES A m e l i o r a t i o n of the b l a c k f l y problem may be sought through v a r i o u s means which are embraced w i t h i n s e v e r a l broad c a t e g o r i e s . The t h e o r e t i c a l as w e l l as the t r i e d approaches to be c o n s i d e r e d may be i d e n t i f i e d as f o l l o w s : P o p u l a t i o n r e d u c t i o n . D i r e c t k i l l i n g of p o p u l a t i o n numbers - A p p l i c a t i o n of l a r v i c i d a l chemicals such as syn-t h e t i c s , p l a n t a l k a l o i d s or i n s e c t growth r e g u l a t o r s . - A p p l i c a t i o n of a d u l t i c i d a l c h e m i c a l s . - Trapping o f a d u l t s by l u r e s such as pheromones, or host a t t r a c t a n t s . ( T h e o r e t i c a l p o s s i b i l i t y f o r l i m i t e d use, un e x p l o r e d ) . M a n i p u l a t i o n o f agents o f b i o t i c c o n t r o l (not t r i e d on an o p e r a t i o n a l s c a l e ) . - I n t r o d u c t i o n , i n u n d a t i o n w i t h , or enhancement o f , predacious or p a r a s i t i c or c o m p e t i t i v e i n s e c t s , nematodes, mites, or b i r d s . - Inundation o f area w i t h s t e r i l e males. - I n t r o d u c t i o n of d e f e c t i v e gene c h a r a c t e r s . M a n i p u l a t i o n o f a q u a t i c h a b i t a t s by mo d i f y i n g flow c h a r a c t e r i s t i c s through impoundments of s t r e t c h e s of water behind dams. Refuges from a t t a c k comprise shaded s h e l t e r s f o r c a t t l e . I n d i v i d u a l p r o t e c t i o n to prevent a t t a c k . Chemical r e p e l l e n t s or d e t e r r e n t s a p p l i e d to s k i n or - 80 c l o t h i n g ; s p e c i a l n u t r i e n t regimes to modify chemical f a c t o r s i n dermal s e c r e t i o n s . P r o t e c t i v e c l o t h i n g t h a t minimizes a t t r a c t i o n , and excludes f l i e s ; head n e t s . Immunization to a v e r t p h y s i o l o g i c a l e f f e c t s of s a l i v a r y t o x i n s i n j e c t e d by f l i e s . (This remains w i t h i n the realm of t h e o r y ) . Therapy f o r b i t e v i c t i m s . T o p i c a l a p p l i c a t i o n s on s k i n a f t e r b i t e s occur. Systemic a d m i n i s t r a t i o n o f a n t i h i s t a m i n e s or other medications (needs r e s e a r c h i n g ) . H o s p i t a l i z a t i o n f o r severe cases of toxaemia or cases o f secondary c o m p l i c a t i o n s from i n f e c t i o n s f o l l o w i n g s c r a t c h i n g . Therapy of f i l a r i a l and oth e r c o n d i t i o n s which are conveyed by b l a c k f l i e s . 6.1 DE-POPULATION One of the t r a d i t i o n a l s t r a t e g i c approaches to a l l e v i a t i o n of the b l a c k f l y problem i s aimed at r e d u c i n g t h e i r p o p u l a t i o n numbers. V a r i o u s t a c t i c a l means are to be c o n s i d e r e d , some o f which have been used on an o p e r a t i o n a l s c a l e , w h i l e others remain as t h e o r e t i c a l p o s s i b i l i t i e s , even i f not yet a p p a r e n t l y t e c h n i c a l l y f e a s i b l e , e c o n o m i c a l l y r e a s o n a b l e , or e n v i r o n m e n t a l l y a c c e p t a b l e . In p r i n c i p l e , p o p u l a t i o n r e d u c t i o n may be sought through chemical agents, b i o l o g i c a l agents, and water management. - 81 -6.1.1 C h e m i c a l l y - i n d u c e d d e - p o p u l a t i o n A wide spectrum of n a t u r a l and s y n t h e t i c i n s e c t i c i d a l substances p r o v i d e s p o s s i b i l i t i e s f o r k i l l i n g the immature a q u a t i c stages and the winged a d u l t s o f b l a c k f l i e s . The chemicals i n c l u d e a wide v a r i e t y o f s y n t h e t i c s such as c h l o r i n a t e d hydrocarbons, carbamates, and organophosphates. I n s e c t i c i d e s of p l a n t o r i g i n such as p y r e t h r i n s , f o r example, are not mentioned. A s p e c i a l category of chemicals which has been the o b j e c t o f t e s t i n g f o r p o s s i b l e c o n t r o l o f b l a c k f l y l a r v a e i n c l u d e d j u v e n i l e hormones (McKague and Wood 1974). Other i n s e c t growth r e g u l a t o r s and t h e i r l a b o r a t o r y - p r o d u c e d analogues might be contemplated. Pheromones or other p o s s i b l e a t t r a c t a n t s f o r l u r i n g and t r a p p i n g b l a c k f l i e s appear yet to be researched. One t h e o r e t i c a l appeal of chemical " c o n t r o l " o f b l a c k f l i e s i s the immediacy of a l l e v i a t i o n r e s u l t i n g from e x t e n s i v e a e r i a l a p p l i c a t i o n o f a d u l t i c i d e s to k i l l the a d u l t p o p u l a t i o n s , and from the i n t r o d u c t i o n o f l a r v i c i d e s i n t o r i v e r s to decimate the immature stages before they can emerge as f l i e s which might spread over great d i s t a n c e s and areas. D.D.T. has been used i n many p a r t s o f the world, i n c l u d i n g West A f r i c a , Canada, the Un i t e d S t a t e s , Mexico and Japan, s i n c e about the beginning of the nin e t e e n f i f t i e s . The f i r s t r e p o r t of t h i s chemical's use f o r b l a c k f l y c o n t r o l i n Canada was 1948 (Hocking et al. 1949). E f f e c t i v e r e s u l t s were claimed with a dosage o f 0.1 ppm f o r 15 minutes. F u r t h e r t e s t s made to compare v a r i o u s f o r m u l a t i o n s o f D.D.T., T.D.E., l i n d a n e , c h l o r d a n e , toxaphene, h e p t a c h l o r , d i e l d r i n , e n d r i n , i s o d r i n , t r i c h l o r o b e n -zene, pyrenone, p a r a t h i o n , m a l a t h i o n and schraden. Only h e p t a c h l o r - 82 -cou l d compete w i t h the e f f i c i e n c y of D.D.T. (Hocking 1950). In those e a r l y days D.D.T. seemed the obvious c h o i c e o f i n s e c t i c i d e with i t s r a p i d e f f e c t i v e n e s s , r e l a t i v e cheapness, and i t s low o r a l mammalian t o x i c i t y . Great c o n t r o l successes were announced f o r D.D.T., yet no a t t e n t i o n was p a i d to any p o s s i b l e s i d e - e f f e c t s d u r i n g t h a t f i r s t decade of i t s use. I n i t i a l t e s t a p p l i c a t i o n s of D.D.T. i n the Saskatchewan R i v e r d u r i n g the summer of 1948 were of a e r i a l l y a p p l i e d 12 pe r c e n t e m u l s i f i a b l e c o n c e n t r a t e o f D.D.T. i n f u e l o i l . Rates of 0.13 and 0.07 ppm D.D.T. f o r 36 and 34 minutes r e s p e c t i v e l y were used. As an example of the f l o w - r a t e of the South Saskatchewan R i v e r , i n t o which the D.D.T. was i n t r o d u c e d , one may c i t e the value given f o r May 25th, 1948 at 8 a.m. as 35,220 c u b i c f e e t / second (997 cu b i c m e t e r s / s e c ) , e q u i v a l e n t to 13.2 m i l l i o n g a l l o n s per minute (60.1 m i l l i o n l i t e r s / m i n u t e ) (Arnason e t al. 1949). The D.D.T. content o f the r i v e r , i n p a r t s per m i l l i o n , at the p o i n t o f a p p l i c a t i o n , was c a l c u l a t e d from the number of pounds of D.D.T. a p p l i e d , d i v i d e d by the volume flow o f the r i v e r at the p o i n t o f a p p l i c a t i o n ( l b s . per minute), m u l t i p l i e d by the time p e r i o d of a p p l i c a t i o n i n minutes. The treatment w i t h 1.13 ppm D.D.T. f o r 36 minutes was e f f e c t i v e irt d e s t r o y i n g b l a c k f l y l a r v a e f o r 17 and p o s s i b l y 90 m i l e s downstream (27.4-145 Km). D.D.T. stream treatments were subsequently adopted by many o r g a n i z a t i o n s concerned w i t h b l a c k f l y i n f e s t a t i o n s . However, i n d i v i d u a l stream treatments i n many areas of Canada are q u i t e u n p r a c t i c a l as there may be l i t e r a l l y thousands o f s m a l l , b l a c k -f l y i n f e s t e d , streams i n any one area o f concern. A l s o , such an - 83 approach i n areas of rugged t e r r a i n , heavy f o r e s t cover, and o f t e n without roads, i s q u i t e o b v i o u s l y beyond economic or p r a c t i c a l c o n s i d e r a t i o n s . Ground-based l a r v i c i d i n g techniques are used more o f t e n than a e r i a l s p r a y i n g i n s m a l l e r and more e a s i l y a c c e s s i b l e a r e a s . In as much as access i s not always p o s s i b l e , a i r c r a f t have a r e c o g n i s e d p l a c e f o r l a r v i c i d e a p p l i c a t i o n s . Kissam et al. (1973) recommended h e l i c o p t e r s i n South C a r o l i n a , i n order to permit slow f l y i n g along r i v e r c o u r s e s , but slow f l i g h t i s not always c o n s i d e r e d necessary, ( C o l l i n s et al. 1952). With ground-based a p p l i c a t i o n s , enough l a r v i c i d e must be put i n t o the r i v e r at one or two p o i n t s to give a s u f f i c i e n t l y h i g h i n i t i a l c o n c e n t r a t i o n f o r the chemical to remain e f f e c t i v e f o r a somewhat extended time. A f t e r the e f f e c t s o f D.D.T. on f i s h and other a q u a t i c l i f e became w e l l documented, a l t e r n a t i v e i n s e c t i c i d e s r e c e i v e d s e r i o u s c o n s i d e r a t i o n i n the l a t e 1960's. When a t o t a l ban was put on-the use of D.D.T. i n Canada, i t s analogue, methoxychlor, took i t s p l a c e , although, not s u r p r i s i n g l y , r e c e n t work has r e v e a l e d t h a t Abate, Dursban and methoxychlor ( a l l 3 have been used s i n c e the banning o f D.D.T.) a l l a d v e r s e l y a f f e c t n on-target i n v e r t e -b r a t e stream fauna such as Ephemeroptera, T r i c h o p t e r a , P l e c o p t e r a and Chironomidae l a r v a e (Wallace et at. 1973). Chemical c o n t r o l s , i n aiming at d i r e c t d e - p o p u l a t i o n , have l i m i t a t i o n s i n h e r e n t i n the widespread d i s p e r s a l of any t o x i c v m a t e r i a l , and i n the p o s s i b i l i t y o f damage to b e n e f i c i a l or non-i n j u r i o u s forms of l i f e . - 84 -D i v e r s e problems are a s s o c i a t e d w i t h , and d e r i v a t i v e from, the l a r v i c i d a l approach. One form o f problem c o n s i s t s o f t e c h n i c a l and f i n a n c i a l l i m i t a t i o n s f o r d e a l i n g w i t h v a s t a r e a s , which a l s o are o f t e n d i f f i c u l t of a c c e s s . Other major o b s t a c l e s c o n s i s t of contamination of water s u p p l i e s , the d i r e c t and i n d i r e c t impact of p e s t i c i d e s on non-target organisms, the p o s s i b i l i t y of a p e s t i c i d e e x e r t i n g a g e n e t i c s e l e c t i o n p r e s s u r e which becomes s e l f - d e f e a t i v e , and the impermanence of treatment. A s i d e from the s i m p l e r l o c a l a p p l i c a t i o n o f l a r v i c i d e s f o r l i m i t e d r e s u l t s , a great problem i n l o g i s t i c s r e s i d e s i n the need to t r e a t l a r g e areas of t e r r i t o r y which are i n t e r l a c e d w i t h streams. The p h y s i c a l problem i s e s p e c i a l l y d i f f i c u l t i n rugged mountainous t e r r a i n . The e f f e c t s of p e s t i c i d e s on non-target organisms may l e a d through v a r i o u s sequences. However, very few c i t a t i o n s on t h i s s u b j e c t may be found i n d i r e c t r e f e r e n c e to b l a c k f l y c o n t r o l . On the other hand, c o n s i d e r a b l e r e l e v a n t l i t e r a t u r e d e r i v e s from s t u d i e s of the e f f e c t s on a q u a t i c l i f e caused by f o r e s t s p r a y i n g f o r c o n t r o l of f o r e s t d e f o l i a t o r s . Hazards may comprise d i r e c t i n j u r i e s to humans, b i r d s and f i s h , or they may accrue from the d e s t r u c t i o n of v a r i o u s u n i - c e l l u l a r and m u l t i - c e l l u l a r p l a n t and animal organisms at d i f f e r e n t t r o p h i c l e v e l s i n the flow of energy through the food c h a i n s . An i n d i c a t i o n of the e f f e c t on phytoplankton of v a r i o u s p e s t i c i d e s , some of which have been, and are being used f o r c o n t r o l of b l a c k f l y l a r v a e i n r i v e r s , i s c l e a r l y noted i n the t a b u l a t i o n given by B u t l e r (1963) (see Appendix of t h i s T h e s i s ) . - 85 -Inasmuch as b l a c k f l y l a r v a e themselves c o n s t i t u t e important primary consumers of u n i - c e l l u l a r organisms (Jones 1948), and at v a r i o u s times and p l a c e s are important d i r e c t c o n s t i t u e n t s of the d i e t a r y o f f i s h , or, p o s s i b l y of di p p e r b i r d s (water o u z e l s ) , and inasmuch as b l a c k f l y l a r v a e a l s o s u s t a i n secondary and t e r t i a r y consumers, a d r a s t i c r e d u c t i o n i n t h e i r numbers by p e s t i c i d e s c o u l d have unwanted | e f f e c t s on the high e r t r o p h i c l e v e l s o f consumers. These e f f e c t s would c o n c e i v a b l y be s e r i o u s r e g a r d l e s s of the p e r s i s t e n c e or t r a n s i e n c e o f the chemical, and r e g a r d l e s s of whether i t s o r i g i n be a c o n v e n t i o n a l s y n t h e t i c , a p l a n t product, or an i n s e c t j u v e n i l e hormone or analogue of same. Where p e r s i s -t e n t i n s e c t i c i d e s might be used, the p r o g r e s s i v e c o n c e n t r a t i o n s along the food c h a i n s , or p r o g r e s s i v e g a t h e r i n g at v a r i o u s p o i n t s along the food c h a i n can become h i g h l y dangerous to the u l t i m a t e consumer organisms such as b i r d s or humans (Ent.'Soc. Canada, 1970). Few papers d e a l w i t h the impact of p e s t i c i d e s as used e x p l i c i t l y f o r b l a c k f l y c o n t r o l . Fredeen et al. (1971) a s s e r t that 20 years o f almost unbroken annual and semi-annual a p p l i c a -t i o n o f D.D.T. i n t o the Saskatchewan R i v e r , f o r b l a c k f l y c o n t r o l , w i t h c o n c e n t r a t i o n s r e a c h i n g 0.1 to 0.3 ppm, s u s t a i n e d f o r 15 minutes i n the volume of water p a s s i n g the a p p l i c a t i o n p o i n t , r e s u l t e d i n D.D.T. r e s i d u e s i n the muscle t i s s u e s o f f i s h i n the range of 0.01 to 0.05 ppm. It was remarked t h a t these concentra-t i o n s were w e l l below the a c t i o n a b l e l e v e l of 5.0 ppm of D.D.T. re s i d u e s i n e d i b l e f i s h . T h i s f i n d i n g , however, does not p r o v i d e f o r other dimensions of the impact which r e l a t e to food chains and biomass p r o d u c t i v i t y of the r i v e r . - 86 -Notwithstanding o p p o r t u n i t i e s a f f o r d e d by some l a r g e - s c a l e and p e r e n n i a l a p p l i c a t i o n s of l a r v i c i d e s to d e s t o r y b l a c k f l y p o p u l a t i o n s i n r i v e r s , v ery l i t t l e c a r e f u l l y documented i n f o r m a t i o n has become a v a i l a b l e on the e f f e c t s of these o p e r a t i o n s on food chains and the b i o l o g i c a l p r o d u c t i v i t y of r i v e r s . High r a t e s o f r e d u c t i o n have been r e p o r t e d to occur among m a y f l i e s (Ephemerop-t e r a ) , c addis f l i e s ( T r i c h o p t e r a ) , stone f l i e s ( P l e c o p t e r a ) , and c e r t a i n s p e c i e s of a q u a t i c b e e t l e s a f t e r l a r v i c i d a l t r e a t -ments a g a i n s t b l a c k f l i e s (Arnason et al. 1949; Hoffmann and Surber 1948; Hynes and W i l l i a m s 1962; McMahon et al. 1958). From these r e p o r t s , the a b i l i t y of non-target organisms to r e p o p u l a t e an area soon a f t e r treatment remains u n c e r t a i n . The impact of l a r v i c i d e s on p o p u l a t i o n s of a q u a t i c organisms and on t h e i r r a t e of r e p o p u l a t i o n must depend upon the s p e c i f i c t o x i c substance, the form i n which i t i s a p p l i e d , the dosage, the extent of area de-populated and the frequency of a p p l i c a t i o n . R e s u l t s on small areas may not p r o v i d e a sound b a s i s f o r e x t r a -p o l a t i n g on l a r g e areas. The data of G j u l l i n et al. (1949) demonstrate the d i f f e r e n -ces i n absolute and r e l a t i v e t o x i c i t i e s of a number of i n s e c t i -c i d e s , and show the importance of f o r m u l a t i o n i n c r e a t i n g a d i f f e r e n t i a l e f f e c t which i s more l e t h a l to b l a c k f l i e s than to other stream organisms. (See Appendix 3). One of the p o s s i b l y u n d e s i r a b l e e f f e c t s of the i n t e n s i v e and e x t e n s i v e a p p l i c a t i o n of n o n - s e l e c t i v e i n s e c t i c i d e s f o r b l a c k f l y c o n t r o l i s that a temporary d e s t r u c t i o n of competitors and p r e d a t o r s may favour a more r a p i d r e c o l o n i z a t i o n by b l a c k f l i e s - 87 than by other organisms. Thus, the b l a c k f l y problem may become i n t e n s i f i e d t e m p o r a r i l y , as suggested by Hynes (I960). Indeed, Davies (1950) had noted a s t r i k i n g resurgence of a b l a c k f l y p o p u l a t i o n i n a stream three years a f t e r i t s treatment w i t h D.D.T. Although a p o s s i b l e c a u s e - a n d - e f f e c t r e l a t i o n s h i p i s presumptive, such a p o s s i b i l i t y m e r i t s f u r t h e r study, w i t h a t t e n t i o n g i v e n to the k i n d of p e s t i c i d e , i t s f o r m u l a t i o n , dosage, e x t e n t , time of year when a p p l i e d , and p h y s i c a l and b i o l o g i c a l f e a t u r e s of the h y d r o l o g i c a l systems. The c o n c e i v a b l e d i r e c t and i n d i r e c t e f f e c t s of p e s t i c i d a l c o n t r o l of b l a c k f l i e s on b i r d l i f e seems not to have been r e p o r t e d . The d i r e c t hazards of p e s t i c i d e s f o r b i r d - l i f e r e s u l t i n g from b l a c k f l y c o n t r o l , might be i n f e r r e d from the g e n e r a l l i t e r a t u r e . There remains to be e x p l o r e d the p o s s i b l e s e l f - d e f e a t i v e n e s s of repeated i n t e n s i v e a p p l i c a t i o n s of i n s e c t i c i d e s a g a i n s t b l a c k -f l i e s , as a r e s u l t of such treatments a c t i n g as a g e n e t i c s e l e c -t i o n p r e s s u r e f a v o r i n g i n s e c t i c i d a l r e s i s t a n c e . However, a v a s t l i t e r a t u r e e x i s t s on the g e n e r a l s u b j e c t as i t r e l a t e s to o t h e r forms o f i n s e c t s , i n c l u d i n g such haematophagous forms as mos-q u i t o e s . Two examples o f l i t e r a t u r e d e a l i n g w i t h the g e n e t i c s of i n s e c t i c i d a l r e s i s t a n c e i n mosquitoes may s u f f i c e here to i n d i c a t e the scope o f the problem: Beard(1965); P e n n e l l and Hoskins (1964). 6.1.2 B i o l o g i c a l c o n t r o l Although non-chemical methods of b l a c k f l y c o n t r o l are being given i n c r e a s i n g l y more a t t e n t i o n , p r o g r e s s i s hampered by problems w i t h mass r e a r i n g techniques and by gaps i n the know-ledge o f b l a c k f l y b i o l o g y and behaviour. Consequently no r e a l 88 -attempts at b i o l o g i c a l c o n t r o l of b l a c k f l i e s have been made to date. However, p r e l i m i n a r y l a b o r a t o r y t r i a l s have been conducted on the i r r a d i a t i o n of mature b l a c k f l y l a r v a e (Gross and Baldwin 1972), but without much success. For the p r i n c i p l e of s t e r i l e male r e l e a s e to be e f f e c t i v e i n mosquito c o n t r o l approximately one m i l l i o n s t e r i l e males per day must be r e l e a s e d to every 50 w i l d males born d a i l y (Laven 1974). With numbers as l a r g e as these i t seems h a r d l y l i k e l y t h a t such methods can be c a l l e d economic, f o r mosquito c o n t r o l , b l a c k f l y c o n t r o l , or any other such pest s p e c i e s . R e c e n t l y a t t e n t i o n has been p a i d to the p o s s i b i l i t y of u t i l i z i n g p a r a s i t i c nematode worms of the genus Mermis as b i o l o g i -c a l c o n t r o l agents f o r b l a c k f l i e s . The n a t u r a l occurrence o f t h i s p a r a s i t e has been r e p o r t e d as c a u s i n g m o r t a l i t i e s as h i g h as 95 percent i n s i m u l i i d broods i n North America (Maser 1973). Before Mermis can be used on the s c a l e n e c e s s a r y i n any b l a c k f l y outbreak a r e a , a p r a c t i c a l mass r e a r i n g technique must be developed f o r these worms. P r e s e n t l y , i n v e s t i g a t i o n s are being d i r e c t e d toward l a b o r a t o r y and f i e l d s t u d i e s of mermithids i n n a t u r a l p o p u l a t i o n of Canadian b l a c k f l i e s , and of r e l e v a n t aspects of b i o l o g y and ecology of these i n s e c t s . 6.1.3 H a b i t a t management Va r i o u s a p p l i c a t i o n s of water management have been attempted, on a small s c a l e , as a form of b l a c k f l y c o n t r o l . Impoundment of streams or r i v e r s w i t h dams w i l l e f f e c t i v e l y modify the hydro-dynamics and water a e r a t i o n of a p o t e n t i a l or e x i s t i n g breeding area, making i t l e s s s u i t a b l e f o r l a r v a e , and t h e r e f o r e l e s s 89 p r o d u c t i v e of b l a c k f l i e s . However, although dam c o n s t r u c t i o n has been attempted as a c o n t r o l measure (Dampf 1931) , i t has r e p o r t e d l y not been very e f f e c t i v e . The reason i s that although dams act to pond-up and reduce the flow along the main course of a r i v e r , thereby c r e a t i n g g e n e r a l l y adverse h a b i t a t c o n d i t i o n s f o r b l a c k -f l i e s , they a l s o p r o v i d e e x c e p t i o n a l l y f a v o u r a b l e b l a c k f l y b r e e d i n g s i t e s i n t h e i r s p i l l w a y s (Peterson and Wolfe 1958) . I t i s c o n c e i v a b l e a l s o that the r e s u l t a n t s u b s t i t u t i o n of q u i e t bodies o f impounded water f o r the t u r b u l e n t f l o w i n g water o f streams c o u l d c r e a t e f a v o u r a b l e h a b i t a t s f o r mosquitoes. M a n i p u l a t i o n which would a l t e r n a t e l y r a i s e and lower the stream l e v e l s i n order to c r e a t e a " f l u s h i n g - a c t i o n " , s u f f i c i e n t to wash the l a r v a e downstream, has been done i n c o n j u n c t i o n w i t h l o g - d r i v e s , which act to g i v e an a d d i t i o n a l b a t t e r i n g a c t i o n (West 1958). However, the e f f e c t s of f l u s h i n g are s h o r t - l i v e d , even i f the stream does possess the f a c i l i t i e s to c o n t r o l i t s flow. 6.2 PERSONAL PROTECTION For the i n d i v i d u a l who may be s u b j e c t e d to plagues o f b l a c k f l i e s , the e a s i e s t form of immediate r e l i e f i s i n the form of p e r s o n a l p r o t e c t i o n with r e p e l l e n t s and s u i t a b l e c l o t h i n g . P r o t e c t i v e c l o t h i n g a g a i n s t b l a c k f l i e s i s p a r t i c u l a r l y popular i n the n o r t h , where work must always be done out of doors d u r i n g the b l a c k f l y season. B l a c k f l i e s are n o t o r i o u s f o r c r a w l i n g under c l o t h i n g , p a r t i c u l a r l y around the w r i s t s , neck and f r o n t openings of s h i r t s and t r o u s e r s . Zippers r a t h e r than buttons can help 90 s l i g h t l y , as a l s o can the c h o ice of l i g h t e r c o l o u r e d c l o t h i n g . Orange, y e l l o w and l i g h t green m a t e r i a l s are l e s s a t t r a c t i v e to b l a c k f l i e s than dark b l u e , p u r p l e and red (Fredeen 1973). However, the p a r t i c u l a r s p e c t r a l composition and wave-length balance i n these c o l o u r s remain u n d e f i n e d . The t e x t u r e of c l o t h i n g f a b r i c s i s a l s o important, as c e r t a i n b i t i n g f l i e s have been shown to be more a t t r a c t e d to s h i n y s u r f a c e s than to d u l l matt ones (Brown 1952). T h i s " p r e f e r e n c e " a l s o draws a t t e n t i o n to the importance of awareness o f the d i f f e r e n c e between s p e c u l a r r e f l e c t a n c e and wide-angle d i f f u s e d r e f l e c t a n c e . S t u d i e s of b l a c k f l y behaviour which i n v o l v e l i g h t , should p r o v i d e f o r t h i s phenomenon. P r o t e c t i v e c l o t h i n g i s n e c e s s a r i l y b u l k y and uncomfortable. Often i t i s d i f f i c u l t to combine the r e q u i r e d c h a r a c t e r i s t i c s o f c l o t h i n g designed as p r o t e c t i o n a g a i n s t both mosquitoes and b l a c k f l i e s , where both may be a problem. The t i g h t f i t t i n g , o f t e n uncomfortable, c l o t h i n g n e c e s s a r y f o r any degree of r e l i e f from b l a c k f l i e s may hinder work progress due to wearer discom-f o r t s . R e p e l l e n t s are o f t e n used i n c o n j u n c t i o n with p r o t e c t i v e c l o t h i n g , e i t h e r a p p l i e d to the f a b r i c or d i r e c t l y to the s k i n . Although s e v e r a l chemicals are l a b e l l e d " r e p e l l e n t s " , they are r e a l l y no b e t t e r than d e t e r r e n t s to f e e d i n g i n that they do not g e n e r a l l y prevent f l i e s from l a n d i n g . The s o - c a l l e d r e p e l l e n t s u s u a l l y show no a c t i o n at even s h o r t d i s t a n c e s from the host and must be a p p l i e d as a complete c o v e r i n g to a f f o r d any degree of p r o t e c t i o n . Chemical d e t e r r e n t s are a l s o a v a i l a b l e to p r o t e c t - 91 -l i v e s t o c k , but as such chemicals u s u a l l y need s p r a y i n g or brushing on d a i l y , e f f e c t i v e c o n t r o l i s n e i t h e r easy nor cheap. F u r t h e r -more, b l a c k f l i e s tend to a t t a c k the un d e r s u r f a c e s o f c a t t l e , so that d e v i c e s f o r e f f e c t i v e s e l f - a d m i n i s t r a t i o n of d e t e r r e n t s have not been designed. The i s s u e o f p e r s o n a l p r o t e c t i o n would be much s i m p l i f i e d , i f i n s t e a d of u s i n g the p r e s e n t l y known g u s t a t o r y d e t e r r e n t s , an o l f a c t o r y r e p e l l e n t would be sought. Progress i s hampered p a r t l y by the l a c k o f a r i g o r o u s study o f b l a c k f l y behaviour i n g e n e r a l , and b l a c k f l y a t t a c k s t r a t e g y s p e c i f i c a l l y . I t i s hampered a l s o by a l a c k o f understanding o f the s p e c i f i c nature o f f a c t o r s i n i n d i v i d u a l hosts which render some f r e e and others h i g h l y a t t r a c -t i v e . I t seems p e r t i n e n t to understand not o n l y the o p e r a t i o n o f the organisms we are t r y i n g to d e t e r , i . e . b l a c k f l i e s , but a l s o what a t t r a c t a n c i e s we are t r y i n g to obscure i n the host. The search f o r d e t e r r e n t s remains l a r g e l y e m p i r i c a l , t r i a l -a n d - error, w i t h some chance f i n d i n g s , and these used as a s t a r t i n g base f o r see k i n g improvement by s y n t h e s i s and t e s t i n g o f analogues. - 92 SUMMA'RY Th i s c r i t i c a l review was undertaken i n the context of the apparent need f o r a p e r s p e c t i v e view of i n f o r m a t i o n r e l a t i n g to b l a c k f l i e s as a m u l t i d i m e n s i o n a l problem, so that judgements might be made as to needs f o r f u r t h e r study and a c t i o n . The pr e s e n t work i s based on an e v a l u a t i o n of 450 l i t e r a t u r e r e f e r e n c e s i n f i v e d i f f e r e n t languages, and some p e r s o n a l i n t e r v i e w s . The l i t e r a t u r e came from more than 200 j o u r n a l s , s p e c i a l r e p o r t s , monographs and textbooks. I t was examined f o r the purpose of e s t a b l i s h i n g the dimensions of the problems r e l a t i n g to b l a c k f l i e s , i n r e s p e c t to t h e i r b i o l o g i c a l a t t r i b u t e s , impacts on v a r i o u s forms of l i f e , impacts on res o u r c e uses and development, r o l e s i n food c h a i n s , problems i n a c h i e v i n g p r o t e c t i o n , and environmen-t a l c o n s i d e r a t i o n s i n seeking c o n t r o l . The l i t e r a t u r e was examined f o r f a c t u a l content, gaps i n i n f o r m a t i o n , d i f f i c u l t i e s i n r e s e a r c h , misunderstandings, reasons f o r such d i f f i c u l t i e s , and examined f o r c o n c e i v a b l e avenues t h a t r e s e a r c h might p r o f i t a b l y take. 93 CONCLUSIONS An e x t e n s i v e and d i v e r s i f i e d l i t e r a t u r e a t t e s t s to the importance and complexity o f the s u b j e c t which dea l s w i t h b l a c k f l i e s . Much of the work done d u r i n g the past two c e n t u r i e s remains v a l i d today, but c e r t a i n p i t f a l l s need to be understood. I n v e s t i -g a t i o n s on b l a c k f l i e s have r e l a t e d to morphology, taxonomy, h i s t o l o g y , morphogenesis, c y t o l o g y , food, r e s p i r a t i o n , b l o o d c i r c u l a t i o n , r e p r o d u c t i o n , d i s p e r s a l , a t t a c k h a b i t s , v a r i o u s aspects o f s a l i v a r y t o x i n s of the f l i e s , t r a n s m i s s i o n of patho-genic micro-organisms and f i l a r i a l worms, s p e c i e s d i s t r i b u t i o n s , h a b i t a t requirements, p r e d a t o r s , p a r a s i t e s , r o l e s i n food c h a i n s , impacts on r e s o u r c e uses and development, undertakings by popu-l a t i o n r e d u c t i o n , and i n d i v i d u a l p r o t e c t i o n by c l o t h i n g and chemical r e p e l l e n t s . Knowledge on the s u b j e c t has l o s t much of i t s p o t e n t i a l impact, and pro g r e s s h i n d e r e d because t h a t knowledge i s p a r t i a l l y obscured i n the depths of time, awkwardly s c a t t e r e d through the l i t e r a t u r e i n d i f f e r e n t languages, compartmentalized i n p u b l i c a -t i o n s addressed to audiences having d i v e r s e t h r u s t s df i n t e r e s t , and sometimes confused and m i s l e a d i n g through disagreements on taxonomic i d e n t i t i e s . The i d e n t i t y o f f a c t o r s , and determinant mechanisms i n a t t r a c t a n c e and r e p e l l e n c e f o r b l a c k f l i e s c o n s t i t u t e a major aspect o f the problems which remain obscure, and the i n f o r m a t i o n m i s l e a d i n g . For v a r i o u s reasons the components of b l a c k f l y behaviour are u n c l e a r because i n v e s t i g a t o r s have not understood - 94 -the p r i n c i p l e s of successive and simultaneous i n d u c t i o n i n i n s e c t behaviour; they d i d not, and do not, understand the physiology and chemistry of e c c r i n e , apocrine and sebaceous s e c r e t i o n s of human s k i n ; and they have not considered the conceivable r o l e of s p e c t r a l r e f l e c t a n c e of the s k i n . Consequently, the reasons f o r host - i n d i v i d u a l d i f f e r e n c e s i n proneness to being attacked cannot yet be explained or manipulated, and progress i n develop-ment of f l y r e p e l l e n t s or de t e r r e n t s proceeds through e m p i r i c a l processes. The mechanisms of d i f f e r e n t i a l r e a c t i v i t y to f l y - b i t e s between host i n d i v i d u a l s , and of changing s u s c e p t i b i l i t y w i t h i n i n d i v i d u a l s , are unclear. Sources of confusion r e s i d e i n unresolved taxonomy, and i n ignorance by some i n v e s t i g a t o r s regarding the nature of mechanisms and requirements,in immunology. Documentation of impacts of b l a c k f l i e s on resource uses and va l u e s , though incomplete, demonstrates that these i n s e c t s create severe problems. B l a c k f l i e s occupy an important place as primary consumers and as consumed organisms i n food chains, so that f o r these reasons i n t e n s i v e depopulation schemes, even i f n o n - p o l l u t i n g , could be damaging to both commercial and sport f i s h e r i e s manager ment. Release of l a r v i c i d e s i n t o r i v e r systems f o r c o n t r o l of b l a c k f l i e s could be hazardous to consumer organisms which depend on b l a c k f l i e s and other aquatic l i f e . Progress i n knowledge, and development of methods f o r v a l l e v i a t i n g the problems have been impeded by a frequent a t t i t u d e of apathy which derives from a f a t a l i s t i c acceptance of misery, - 95 -e s p e c i a l l y by those who do not s u f f e r i t , and by an ignorance of b l a c k f l y behaviour, ignorance of the chemical, p h y s i c a l , p h y s i o -l o g i c a l , and g e n e t i c determinants of host r e s i s t a n c e and s u s c e p t i b i l i t y , a fragmented, t a c t i c a l approach to the problems, the c h a n e l l i n g o f funds and e f f o r t s i n t o outmoded p r a c t i c e s , or i n t o r e s e a r c h which merely seeks to modify d e t a i l s of o l d concepts, or p u r s u i t o f l i n e s which seek o n l y l o c a l b e n e f i t s , and f a i l u r e i n attempts to r e a r b l a c k f l i e s under l a b o r a t o r y c o n d i t i o n s . t o serve the needs of exp e r i m e n t a t i o n w i t h stock of known h i s t o r y . Much remains to be done, but the d i r e c t i o n s which might p r o f i t a b l y be taken should become c l e a r e r by a study of p o i n t s h i g h l i g h t e d i n the p r e s e n t t h e s i s . - 9 6 -APPENDIX I C h e c k l i s t of the b l a c k f l y species r e f e r r e d to i n the t e x t . Genus: Simulium L a t r i e l l e 1802 Species: aroticum aureum ornatum baffinense columbaschense columbaozense damnosum decorum d e f o l i a r t i euryadminioulum jenningsi me latum meridionale metallicum ovioeps pecuarum reptans rugglesi venustum vittatum vulgare woodi Eusimulium aureum pecuarum Cnephia orozetense peouarum Prosimulium peouarum Austrosimulum ungulatum Wi Ihelmia equina Odagmia ornata Malloch F r i e s Meigen Twinn F a b r i c i u s Schonbauer Theobald Walker Davies Malloch Wharton R i l e y B e l l a r d i Edwards R i l e y ( r e f e r r e d to by Rempel and Arnason 1947). Linne Nicholson and M i c k e l Say Z e t t e r s t e d t Rubzov de M e i l l o n Roubaud 1906 F r i e s ( R i l e y ) ( r e f e r r e d to by Bradley 1935) E n d e r l e i n 1921 (Womersley) ( R i l e y ) ( r e f e r r e d to by Crosskey 1973) Roubaud 1906 R i l e y ( r e f e r r e d to by M a l l o ch 1914) Tonnoir 1925 Tonnoir E n d e r l e i n 1922 Linne E n d e r l e i n 1921 Edwards - 97 -APPENDIX 2. Percentage decrease in pro d u c t i v i t y of natural phytoplankton communities during a 4-hour exposure to a concentration of 1.0 ppm of the indicated i n s e c t i c i d e . Pesticide Percent decrease Pesticide Percent decrease Chlorinated Herbicides hydrocarbons 2,4-D acid 0 A l d r i n 84.6 2,4,5-T acid 0 Chlordane 94.0 2,4-D dimethylamine DDT 77.2 s a l t 0 D i e l d r i n 84.8 Diuron 87.4 Endrin 46.0 Eptam 0 Heptachlor 94.4 Fenuron 40.9 Kepone 94.7 MCP amine weed k i l l e r Lindane 28.5 (formulation) 0 Methoxychlor 80.6 Monuron 94.1 Mi rex 41.6 Neburon 89.9 Thiodan 86.6 Ti l l a m 23.8 Toxaphene 90.8 Fungicides Organophosphorus in s e c t i c i d e s Chemagro 2635 Dyrene 85.3 91.3 ASP-51 29.5 Ferbam 97.0 Bayer 29493 (Baytex) 7.2 Phaltan 31.9 Bayer 25141 0 Diazinon Dibrom Di-Syston 6.8 55.6 55.2 Chlorinated acaricides Dylox Ethion Guthion 0 69.0 0 Sulphonone Tedion 12.2 39.0 Imidan 7.7 Malathion 7.0 S o i l fumigants Meta-Systox R 0 Methyl t r i t h i o n 85.9 Dexon 14.6 Systox 7.11 Nemagon 5.0 Carbamates Bayer 37344 38.7 Bayer 39007 0 Bayer 44646 0 Sevin 16.8 From: Butler, P.A. 1963. - 98 -APPENDIX 3 I n s e c t i c i d e t o x i c i t y l e v e l s f o r a q u a t i c i n s e c t s and f i s h . Organism and To l e r a n c e L e v e l B l a c k f l i e s : Rainbow C a d d i s f l i e s : Minimum Tro u t : Maximum To x i c a n t and Formulation e f f e c t i v e Maximum n o n l e t h a l dosage n o n l e t h a l p.p.m. p. p. m. p. p .m. DDT Emulsion 0.7 3. 5. Acetone s o l u t i o n 0.3 30. 10. Wettable powder 1. 10. 10. F u e l - o i l s o l u t i o n 0.4 10. 10. Kerosene s o l u t i o n 0.3 0.3 .0.3 Gamma BHC Emulsion 1. 1. 0.1 Acetone s o l u t i o n 0.5 10. 10. C h l o r i n a t e d Camphene Emulsion 4. 3. 5. Acetone s o l u t i o n 0.5 5. 0.5 F u e l - o i l s o l u t i o n 0.5 0.5 0.5 A l k y l a t e d naphthalene s o l u t i o n 1.5 1.5 1.5 Chlordane Emulsion 4. 3. 5. Acetone s o l u t i o n 0.5 20. 10. F u e l - o i l s o l u t i o n 0.5 6. 0.5 Commercial s o l v e n t 1.5 10. 1. Pyrethrum Acetone mixture 0.1 0.1 Kerosene s o l u t i o n 0.1 0.1 0.1 T h i s t a b l e shows d i f f e r e n c e s between i n s e c t i c i d e s i n t h e i r t o x i c i t y to the d i f f e r e n t organisms; and d i f f e r e n c e s between forms of p r e p a r a t i o n . The i n f l u e n c e of s o l v e n t on the a b s o l u t e and r e l a t i v e t o x i c i t y o f i n s e c t i d e v a r i e s w i t h the i n s e c t i c i d e . From: G j u l l i n et al. 1949. - 99 -GLOSSARY OF TERMS ANAPHYLACTIC SHOCK - An antigen-antibody reaction. The condi-t i o n of being hypersensitive to a serum or foreign pro-t e i n , caused by a f i r s t or s e n s i t i s i n g dose. ANAUTOGENOUS - I n a b i l i t y to obtain reproductive maturity without a p r i o r blood meal. ANTHOPHILIC - attracted to, and feeding on, nectar and/or pollen. ANTHROPOPHILIC - Attracted to, and feeding on, humans. APOCRINE SECRETIONS - Secretions of viscous type sweat from sweat glands with a d i s t i n c t type of secretory c e l l , the duct of which usually opens into an adjacent hair f o l l i c l e . ECCRINE SECRETIONS - Secretions of a more watery nature from sweat glands with a d i s t i n c t kind of secretory c e l l not associated with hair f o l l i c l e s . Such sweat glands are p a r t i c u l a r l y abundant in the h a i r l e s s regions such as palms, soles, forehead, etc. ENVENOMIZATION - The i n j e c t i o n of toxic substances. HAPTENIC SUBSTANCE - A substance which when combined with a pro-t e i n has the power to confer s p e c i f i c antigenic properties on that protein. MAMMALOPHILIC - Attracted to and feeding on mammals. PASSIVE IMMUNITY - A condition of non-reactivity without the involvement of an antigen-antibody reaction. PNEUMOHYDRORRHOEA - Drowning from f l u i d s within the lungs. SPECULAR REFLECTANCE - The r e f l e c t i o n of l i g h t from polished surfaces in which the angle of r e f l e c t e d l i g h t i s equal to the angle of incident l i g h t . SUCCESSIVE INDUCTION - The i n h i b i t i o n of one response by another response i . e . one' a c t i v i t y of the insect i s influenced by the previous a c t i v i t y . WIDE-ANGLE DIFFUSED REFLECTANCE - The r e f l e c t i o n of l i g h t from d u l l surfaces in which the l i g h t i s scattered uniformly in a l l d i r e c t i o n s . - 100 -LITERATURE CITED Anderson, J.R., V.H. Lee, S. Vadlamudi, R.P. Hanson, and G.R. D e f o l i a r t . 1961. I s o l a t i o n of e a s t e r n e n c h e p a l i t i s v i r u s from D i p t e r a i n Wisconsin. Mosq. News 2_1: 244-248. Arnason, A.P., A.W.A. Brown, F.J.H. Fredeen, W.W. Hopewell, and J.G. Rempel. 1949. Experiments i n the c o n t r o l of Simulium arctioum M a l l o c h by means of D.D.T. i n the Saskatchewan R i v e r . S c i . Agr. 2£: 527-537. A u s t i n , F .J. 1967. The a r b o r i v u s v e c t o r p o t e n t i a l of a s i m u l i i d . Ann. Trop. Med. P a r a s i t . 61: 189-199. Baranov, N. 1937. Die Kolumbatscher Mucke i n Jugoslawien im Jah r e . Arch. T i e r h e i l k . 72_: 158-164. Basrur, P.K. 1959. The s a l i v a r y gland chromosomes of 7 segregates ( D i p t e r a : Simuliidae) w i t h a transformed centromere. Can. J . Z o o l . 37_: 527-570 . Basrur, V.R., and K. R o t h f e l s . 1959. T r i p l o i d y i n n a t u r a l p o p u l a t i o n s of the b l a c k f l y Cnephia mutata ( M a l l o c h ) . Can. J . Z o o l . 37_: 571-589. B a s s l e r , U. 1958. Versuche zur O r i e n t i e r u n g der Stechmucken: Die schwarmbildung und d i e Bedeutung des Johnstonschen organs. Z. V e r g l . P h y s i o l . 41_: 300-330. Beard, R.L. 1965. Competition between D . D . T . - r e s i s t a n t and s u s c e p t i b l e house f l i e s . J . Econ. Ent. 5_8 (3) : 584. Bennett, G.F., A.M. F a l l i s and A.G. Campbell. 1972. The response of Simulium (Eusimulium) euryadminioulum ( D i p t e r a : Simuliidae) to some o l f a c t o r y and v i s u a l s t i m u l i . Can. J . Z o o l . _50: 793-800. Bradbury, W.C., and G.F. Bennett. 1974 a. Behaviour of a d u l t Simuliidae (Diptera) I. Response to c o l o u r and shape. Can. J . Z o o l . 5_2_: 251-258 . Bradbury, W.C., and G.F. Bennett. 1974 b. Behaviour of a d u l t Simuliidae (Diptera) I I . V i s i o n and o l f a c t i o n i n near o r i e n t a t i o n and l a n d i n g . Can. J . Z o o l . 5_2_: 1355-1364. Bradley, G. 1935. Notes on the southern b u f f a l o gnat, Eusimulium pecuarum. Proc. Ent. Soc. Wash. 3_7_: 60-64. . Brouwer, R. 1960. The a t t r a c t i o n of C O 2 e x c r e t e d by the s k i n o f * the arm f o r m a l a r i a mosquitoes. T r o p i c a l Geographical Medicine. 12: 62-66. - 101 -Brown, A.W.A. 1951. Stu d i e s on the responses o f the female Aedes mosquito. Part IV: F i e l d experiments on Canadian s p e c i e s . B u l l . Ent. Res. 42: 575-582. Brown, A.W.A. 1952. F a c t o r s i n the a t t r a c t i v e n e s s of bodies f o r mosquitoes. Trans. N i n t h Int. Congr. Ent. 1: 895-900. Brown, A.W.A. 1956. F a c t o r s which a t t r a c t Aedes mosquitoes to humans. Proc. 10th I n t . Congr. Ent. Mo n t r e a l . 1956. (3): 757-63. Brown, A.W.A. 1966. The a t t r a c t i o n of mosquitoes to h o s t s . J . Am. Med. Assoc. 196: 249-252. Brown, A.W.A. and A.G. Carmichael. 1961. L y s i n e and a l a n i n e as mosquito a t t r a c t a n t s . J . Econ. Ent. 54_: 317-324. Brown, A.W.A., D.S. S a r k a r i a , and R.P. Thompson. 1951. S t u d i e s on the responses of female Aedes mosquito. Part I: The search f o r a t t r a c t a n t vapours. B u l l . Ent. Res. 42_: 105-112. B u t l e r , P.A. 1963. P e s t i c i d e - w i l d l i f e s t u d i e s . U.S. Dept. I n t . F i s h and W i l d l i f e c i r c u l a r #167. Cameron, A.E. 1918. Some b l o o d - s u c k i n g f l i e s o f Saskatchewan. Agr. Gaz. Canada. 5_: 556-561. Cameron, A.E. 1922. The morphology and b i o l o g y of a Canadian c a t t l e i n f e s t i n g b l a c k f l y , Simulium simile M a l l . ( D i p t e r a , Simuliidae) . Canada Dept. Agr. B u l l . _5: (Ent. B u l l . 20), 26 pp. C a r l s s o n , G. 1962. Stu d i e s on Scandinavian b l a c k f l i e s . Opuscula E n t o m o l o g i c a l Supplementum 21. Entomologiska S a l l s k a p e t Lund. C i u r e a , T. and G. D i n u f l e s c u . 1924. Ravages causes par l a mouche de goloubatz en Roumanie; ses attacques c o n t r e l e s animaux et contre l'homme. Ann. Trop. Med. § P a r a s i t . 18: 323-24. C o l l i n s , D.L., B.V. T r a v i s , and H. Jamnback. 1952. T h e ' a p p l i c a -t i o n o f l a r v i c i d e by a i r p l a n e f o r c o n t r o l of b l a c k f l i e s . Mosq. News. 1_2 : 75-77 . C r a i g , D.A. 1974. The labrum and c e p h a l i c fans of l a r v a l Simuliidae ( D i p t e r a : Nematocera). Can. J . Zo o l . 52#1: 133-159. Crosskey, R.W. 1973. Insec t s and other arthropods of medical importance. Chapter 3: Simuliidae. B r i t i s h Museum (Na t u r a l H i s t o r y ) London. E d i t e d by Kenneth G.V. Smith, 1973. Crumb, S.E. 1922. A mosquito a t t r a c t a n t . Science #1426: 446-447. - 102 -Curt i s , L.C. 1954. Observations on a b l a c k f l y pest of c a t t l e in B r i t i s h Columbia. Ent. Soc. B.C. Proc. 51_: 3-7. Dampf, A. 1931. Los simulidos transmisores de l a oncocercosis en los Estados de Oaxaca y chiapis. Medicina (Mex.) 11: 735-761. Davies, D.M. 1951. Some observations on the number of b l a c k f l i e s landing on coloured cloths. Can. J. Zool. 2_9: 65-70. Davies, D.M. 1960. Colour affects the landing of blood-sucking b l a c k f l i e s (Diptera: Simuliidae) on t h e i r hosts. Proc. Ent. Soc. Ont. 91_: 267-268. Davies, D.M. 1972. Landing of blood-seeking female b l a c k f l i e s on coloured materials. Proc. Ent. Soc. Ont. 102: 124-135. Davies, D.M. and B.V. Peterson. 1956. Observations on the mating feeding ovarian development and o v i p o s i t i o n i n adult black-f l i e s . Can. J . Zool. 34: 615-655. Dunbar, R.W. 1959. The s a l i v a r y gland chromosomes of 7 forms of b l a c k f l i e s included in Eusimulium aureum F r i e s . Can. J. Zool. 37_: 495-525. Dyar, H.G. and R.C. Shannon. 1927. The North American two-winged f l i e s of the family Simuliidae. Proc. U.S. Nat. Mus. 69(10): 1-54. Edwards, F.W. 1915. On the B r i t i s h species of Simulium. I. The adults. B u l l . Ent. Res. 6_: 23-42. Edwards, F.W. 1921. On the B r i t i s h species of Simulium. Pt. I I . The early stages, with corrections and additions to Pt. I. B u l l . Entom. Res. 11} 215. E i c h l e r , D.A. and G.S. Nelson. 1971. Studies on Onchocerca gutturosa and i t s development i n S. ornatum. I: - observa-tions on 0. gutturosa in c a t t l e in S.E. England. J . Helminth 45(2/3): 245-258. Enderlein, G. 1922. Weitere Beitrage zur Kenntnis der Simuliidae. Konowia I. Wien. Ent. Soc. Canada. 1970. Pesticides and the Environment B r i e f , B u l l . Ent. Soc. Can. 3_(1) : 1-14. F a l l i s , A.M. 1964. Feeding and related behaviour of female Simuliidae.' Exp. P a r a s i t o l . 1_5: 439-470. F a l l i s , A.M., G.F. Bennett, G. Griggs and T. A l l e n . 1967. C o l l e c t i n g Simulium venustum females i n fan traps and on silhouettes with the aid of C0 o. Can. J . Zool. 45: 1011-1017. - 103 -F a l l i s , A.M. and S.M. Smith. 1964. Ether e x t r a c t s from b i r d s and CO2 as a t t r a c t a n t s f o r some o r n i t h o p h i l i c s i m u l i i d s . Can. J . Z o o l . 42_: 723-730. Fredeen, F.J.H. 1961. A t r a p f o r s t u d y i n g the a t t a c k i n g be-haviour o f b l a c k f l i e s , Simulium avoticum M a l l . Can. Ent. 93(1): 73-78. Fredeen, F.J.H. 1963. O v i p o s i t i o n i n r e l a t i o n to the accumula-t i o n o f blood t h i r s t y b l a c k f l i e s . (Simulium (Gnus) avoticum M a l l . D i p t e r a ) . Nature (Lon.) 200. 4910: 1024. Fredeen, F.J.H. 1973. " B l a c k f l i e s " . Canadian Dept. A g r i c . P u b l i c #1499 (1973) . Fredeen, F.J.H. 1974. T e s t s w i t h s i n g l e i n j e c t i o n s o f methoxy-c h l o r b l a c k f l y l a r v i c i d e s i n l a r g e r i v e r s . Can. Ent. 106: 285-305. Fredeen, F.J.H., J.G. Rempel, and A.P. Arnason. 1951. Egg l a y i n g h a b i t s , o v e r w i n t e r i n g stages and l i f e - c y c l e o f Simulium avoticum M a l l . Can. Ent. <S_3 (3) : 73-76. Fredeen, F.J.H., J.G. Saha, and L.M. Royer. 1971. Residues o f D.D.T., D.D.E., and D.D.D. i n f i s h i n the Saskatchewan R i v e r a f t e r u s i n g D.D.T. as a b l a c k f l y l a r v i c i d e f o r 20 y e a r s . J . F i s h . Res. Bd. Canada 2_8: 105-109. G e o r g e v i t c h , J . 1923. No u v e l l e s recherches sur l a mouche de Goloubatz. Comptes Rendus Hebdomadaires des seances Academie des s c i e n c e s ( P a r i s ) . 176: 1500-1502. G j u l l i n , CM., A.B. Cope, B.F. Quisenberry and F.R. Du Chamois. 1949. The e f f e c t s o f some i n s e c t i c i d e s on b l a c k f l i e s l a r v a e i n Alaskan streams. J o u r . Econ. Ent. 42_: 100-106. Gnedina, M.P. 1959. Economic l o s s e s caused by o n c h o c e r c i a s i s i n c a t t l e . B y u l l e t e n Nauchno - T e k h n i c h e s k o i I n f o r m r a t s i i Vsesoyuznugo I n s t i t u t a G e l m i n t h o l o g i i Im. K.I. Skry a b i n a . #5: 11-16. Graham, K. 1959. Release by f l i g h t e x e r c i s e of a chemotropic response from p h o t o n o s i t i v e domination i n a s c o l y t i d b e e t l e . Nature 184: 283-284*. Gross, H.P., W.F. Baldwin, and A.S. West. 1972. I n t r o d u c t o r y s t u d i e s on the use of r a d i a t i o n i n the c o n t r o l of b l a c k f l i e s . Can. Ent. 104(8): 1217-1222. Gudgel, E.G. and F.H. Graver. 1954. Acute and c h r o n i c r e a c t i o n s to b l a c k f l y b i t e s (Simulium f l y ) . A rch. Dermatol. S y p h i l o l . 70: 609-615. Herms, J.M.T. 1969. M e d i c a l Entomology. New York M c M i l l a n P r e s s . - 104 -H i e r , S.W., T. Cornbeet, and 0. Bergeimo. 1946. The amino a c i d s of human sweat. J . B i o l . Chem. 166: 327-333. Hocking, B. 1950. F u r t h e r t e s t s of i n s e c t i c i d e s a g a i n s t b l a c k f l y and a c o n t r o l procedure. S c i . A g r i c . 3_0: 489-508. Hocking, B. 1952. P r o t e c t i o n from n o r t h e r n b i t i n g f l i e s . Mosq. News. 1_2_: 91-102. Hocking, B. 1971. Blood sucking behaviour of t e r r e s t r i a l a r t h r o -pods. Ann. Rev. Entomol. 16_: 1-26. Hocking, B. and L.R. P i c k e r i n g . Observations on the bionomics of some n o r t h e r n s p e c i e s of Simuliidae. Can. J . Z o o l . 32_: 99-119. Hocking, B., C R . Twinn, and W.C. McDuffie. 1949. A p r e l i m i n a r y e v a l u a t i o n of some i n s e c t i c i d e s a g a i n s t immature stages of b l a c k f l i e s . S c i . A g r i c . 29_: 69-80. Hoffmann, C H . and E.W. Surber. 1948. E f f e c t s o f wettable • D.D.T. on f i s h and f i s h food organisms i n Black Creek, West V i r g i n i a . Trans. Am. F i s h . Soc. 7_5: 41-43. Hynes, H.B.N, and T.R. W i l l i a m s . 1962. The e f f e c t o f D.D.T. on the fauna of a c e n t r a l A f r i c a n stream. Ann. Trop. Med. P a r a s i t . 56^(1): 78-91. James, H.G. 1968. B i r d p r e d a t i o n on b l a c k f l y l a r v a e and pupae i n O n t a r i o . Can. J . Z o o l . 46: 106-107. Jamnback, M. 1973. Recent developments i n c o n t r o l o f b l a c k f l i e s . Ann. Rev. Ent. 18: 281-304. Jones,-J.R.E. 1949. The fauna of f o u r streams i n the 'black mountain' d i s t r i c t o f South Wales. J . Anim. E c o l . 17: 51-65. K e l l o g g , F.E. 1970. Water vapour and CO2 r e c e p t o r s i n Aedes aegypti (L.) J . I n s e c t . P h y s i o l . 1_6: 99-108. Kennedy, J.S. and C O . Booth. 1963. C o - o r d i n a t i o n of s u c c e s s i v e a c t i v i t i e s i n an aphid. The e f f e c t s o f f l i g h t on the s e t t l i n g responses. J . Exp. B i o l . 41_: 805-824 . Kissam, J.B., R. Noblet, and H.S. Moore. 1973. F i e l d e v a l u a t i o n of abate l a r v i c i d e f o r c o n t r o l o f an area endemic f o r Leucocytozoon smithi o f Turkeys. J . Econ. Ent. 66(2) : 426-428. L a i r d , M. 1972. A n o v e l attempt to c o n t r o l b i t i n g f l i e s w ith t h e i r own d i s e a s e . Science Forum 3_0(5) #6: 12-14. Laven, H. 1974. Genetic c o n t r o l o f mosquitoes. T a l l Timbers Conf. on E c o l . Anim. C o n t r o l by H a b i t a t Man. 19-26. - 105 -Lewis, D.J. 1957. Aspects of the s t r u c t u r e , b i o i o g y and study of S. damnosum. Ann. Trop. Med. § P a r a s i t . 51:340-558. L i p s i t z , E.Y. and A.W.A. Brown. 1964. Studies on the responses of the female Aedes mosquito. IX. The mode of a t t r a c t i v e -ness of l y s i n e and other amino ac i d s . B u l l . Ent. Res. 54 : 675-687 . M a l l o c h , J.R. 1914. American b l a c k f l i e s or b u f f a l o gnats. U.S. Dept. Agr. Bur. Ent. Tech. Ser. 26. . M a r l i e r , G. 1952. F i s h feeding on Simulium l a r v a e . Nature 170: 496. Maser, E. 1973. Disease spreading b l a c k f l i e s under a t t a c k at Memorial. S c i . Dimen. 5_(4) : 3-7. Matheson, R. 1950. Medical Entomology - Comstock P u b l i s h i n g Co. Inc. Ithaca, N.Y. McMahon, J.P., R.B. Highton, and H. Goiny. 1958 . The e r a d i c a -t i o n of Simulium neavei from Kenya. B u l l . Wld. H l t h . Org. 31: 669-677. Mercer, K.L. and S.B. Mclver. 1973 a. S e n s i l l a on the palps of se l e c t e d b l a c k f l i e s ( D i p t e r a : Simuliidae'). J . Med. Ent. 10_ #3 : 236-239. M i l l a r , J.L. and J.G. Rempel. 1944. Li v e s t o c k l o s s e s i n Saskat-chewan due to b l a c k f l i e s . Can. J . Comp. Medecine 8_(12) : 334-337. Mundie, J.H. 1968. E c o l o g i c a l i m p l i c a t i o n s on the d i e t of j u v e n i l e coho i n streams. Symp. on salmon and t r o u t i n streams. H.R. MacMillan Lectures i n F i s h e r i e s , U.B.C. pp. 135-153. N i i m i , D. and I. Kuono. 1954. Studies on 'kose' or 'wahi' disease i n c a t t l e . I I . E t i o l o g i c a l i n v e s t i g a t i o n s . B u l l . Fac. A g r i c . Kagoshima Univ. #3_: 151-162. Parker, A.H. 1948. S t i m u l i i n v o l v e d i n the a t t r a c t i o n of Aedes aegypti L. to man. B u l l . Ent. Res. 3_9: 387-397. P e n n e l l , J.T. and W.M. Hoskins. 1964. The mon o f a c t o r i a l i n h e r i t a n c e of r e s i s t a n c e to d i e l d r i n i n l a r v a l and adul t Culex quinquefasciatus Say. B u l l . Wld. H l t h . Org. 31: 669-677. Peschken, D.P. and A.J. Thorsteinson. 1965. V i s u a l o r i e n t a t i o n of b l a c k f l i e s {Simuliidae: Diptera) to c o l o u r , shape and movement of t a r g e t s . Entomol. Exp. Appl. 8_: 282-288. - 106 -Peterson, B.V. 1960. Some n a t u r a l enemies of Utah b l a c k f l i e s . Can. Ent. 9_2 (4) : 266-274. Peterson, B.V. 1970. The Prosimulium of Canada and A l a s k a . Mem. Ent. Soc. Can. #69. Peter s o n , D.G. and A.W.A. Brown. 1951. St u d i e s on the responses of the female Aedes mosquito. Part I I I . The response o f Aedes aegypti (L) to a warm bodv and i t s r a d i a t i o n . B u l l . Ent. Res. 42_: 535-541. Pet e r s o n , D.G. and L.S. Wolfe. 1958. The b i o l o g y and c o n t r o l of b l a c k f l i e s ( D i p t e r a : Simuliidae) i n Canada. Proc. 10th Int . Congr. Ent. Montreal 3_: 551-564. Rempel, J.G. and A.P. Arnason. 1947. An account o f 3 s u c c e s s i v e outbreaks o f the b l a c k f l y Simulium arotioum, a s e r i o u s l i v e s t o c k pest i n Saskatchewan. S c i . A g r i c . 27:428-445. Reuter, J . 1936. O r i e n t e e r e n d onderzoek naar de oorzaak van het gedrag van Anopheles maoulipennis Meigen. b i j de voedselkeuze. (Ser. B) 24: 223-225). Ross, H.H. 1965. A textbook of entomology. 3rd E d i t o n . John Wiley and Sons, Inc. R o t h f e l s , K.H. and R.W. Dunbar. 1953. The s a l i v a r y gland chromosomes o f the b l a c k f l y Simulium vittatum Z e t t . Can. J . Z o o l . 3_1: 226-241. Rubzow, J.A. 1959-1962. Die F l i e g e n der P a l a r k t i s c h e n Region, pp. 1-67. E d i t e d by E. L i n d e r . R u d o l f s , W. 1922. Chemotropism o f mosquitoes. N. J e r s e y A g r i c . Exp. S ta. B u l l . 367: 1-23. S i p p e l l , W.L. and A.W.A. Brown. 1953. St u d i e s on the responses o f the female Aedes mosquito. Part V. The r o l e o f v i s u a l f a c t o r s . B u l l . Ent. Res. 4_3: 567-574. Skinner, W.A., H. Tong, T. Pearson, W. Strauss and H. Maibach. 1965. Human sweat components a t t r a c t i v e to mosquitoes. Nature 207(4997): 661-662. Smart, J . 1945. The c l a s s i f i c a t i o n o f the Simuliidae. Trans. R. Ent. Soc. Lon. 95. Smart, M.R. and A.W.A. Brown. 1956. S t u d i e s on the responses o f female Aedes mosquito. V I I . The e f f e c t o f s k i n tempera-ture hue, and moisture on the a t t r a c t i v e n e s s of the human hand. B u l l . Ent. Res. 47: 89-100. S n i d e r , E.C. 1958. B l a c k f l y c o n t r o l at Mont A p i c a , Quebec. Pulp. Paper Mag. Can. 59(2): 93-106. - 107 Steward, J.S. 1937. The occurrence of Onchocerca gutturosa Newmann i n c a t t l e i n England, w i t h an account of i t s l i f e h i s t o r y and development i n Simmulium ornatum Mg. P a r a s i t . 29_: 212-218. Stokes. 1914. A c l i n i c a l , p a t h o l o g i c a l and experimental study of the l e s i o n s caused by the b i t e of the " b l a c k f l y " Simulium venustum. J . Cutan. D i s . 3_2_: 751-769., 830-856. S t r i c k l a n d , E.H. 1913. Some p a r a s i t e s of Simulium l a r v a e and t h e i r p o s s i b l e economic v a l u e . Can. Ent. 4_5: 405-414. Symes, C.B., R.C.M. Thompson and J.R. Busvine. 1962. Insect c o n t r o l i n p u b l i c h e a l t h . Chapter 12: - O n c h o c e r c i a s i s and simulium f l i e s . E l s e v i e r P u b l i s h i n g Company, N.Y. Thompson, R.C.M. and A.W.A. Brown. 1955. The a t t r a c t i v e n e s s o f human sweat to mosquitoes and the r o l e of carbon d i o x i d e . Mosq. News. 1_5: 80-84. Tucker, R.K. and D.G. C r a b t r e e . 1970. Handbook of t o x i c i t y o f p e s t i c i d e s to w i l d l i f e . U.S. Dept. I n t . F i s h and W i l d l i f e Serv. Resource p u b l . 8_4: 1-131. Twinn, C R . 1939. Notes on some p a r a s i t e s and p r e d a t o r s o f b l a c k f l i e s . Can. Ent. 7_1: 101-102. Wallace, R.R., A.S. West, A.E.R. Downe and H.B.N. Hynes. 1973. The e f f e c t s o f experimental b l a c k f l y l a r v i c i d e s w i t h Abate, Dursban, and Methoxychlor on stream i n v e r t e b r a t e s . Can. Ent. 105(6): 817-833. Waters, T.F. 1968. I n v e r t e b r a t e d r i f t - e c o l o g y and s i g n i f i c a n c e to stream f i s h e s . Symp. on salmon and t r o u t i n streams. H.R. MacMillan Lectures i n F i s h e r i e s , U.B.C. 1969: 121-135 Weiser, J . 1964. P a r a s i t o l o g y of b l a c k f l i e s . B u l l . W.H.O. 31: 483-485. Wenk, P. and J.N. Raybould. 1972. Mating, b l o o d - f e e d i n g and o v i p o s i t i o n o f S. damnosum i n the l a b o r a t o r y . B u l l . W.H.O. 47_(5) : 627-634. West, A.S. 1958. B i t i n g f l y c o n t r o l manual. Pulp and Paper Research I n s t , o f Canada - Mo n t r e a l . Woodlands Research Index #104. W.H.O. 1966. Expert committee on o n c h o c e r c i a s i s 2nd r e p o r t . Tech. Rep. Ser. W.H.O. #335: 1-96. W i l l i s , E.R. 1947. The o l f a c t o r y responses o f female mosquitoes Jour. Econ. Ent. 40: 769-778. - 108 -W i l l i s , E.R. and L.M. Roth. 1952. Reactions of Aedes aegypti to carbon d i o x i d e . J . Exp. Z o o l . 121: 149-179. Wood, D.M., B.V. Peterson, D.M. Davies and H. Gvorkos. 1962. The b l a c k f l i e s of O n t a r i o . Pt. I I . L a r v a l i d e n t i f i c a t i o n w i t h d e s c r i p t i o n s and i l l u s t r a t i o n s . Proc. Ent. Soc. Ont. 9_3: 99-130. Wood, P.W.M. and R.H. Wright. 1968. Some responses of f l y i n g Aedes aegypti to v i s u a l s t i m u l i . Can. Ent. 100 (5) : 504-513. Yang, Y.J. and D.M. Davies. 1974. The s a l i v a r y f l u i d of a d u l t b l a c k f l i e s . Can. J . Z o o l . 52_(6) : 749-751. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0075115/manifest

Comment

Related Items