UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Electron microscopic studies of antennal sensilla in the ambrosia beetle Trypodendron lineatum (Olivier)… Moeck, Henry A. 1967

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

Item Metadata

Download

Media
831-UBC_1967_A6_7 M54.pdf [ 18.17MB ]
Metadata
JSON: 831-1.0104522.json
JSON-LD: 831-1.0104522-ld.json
RDF/XML (Pretty): 831-1.0104522-rdf.xml
RDF/JSON: 831-1.0104522-rdf.json
Turtle: 831-1.0104522-turtle.txt
N-Triples: 831-1.0104522-rdf-ntriples.txt
Original Record: 831-1.0104522-source.json
Full Text
831-1.0104522-fulltext.txt
Citation
831-1.0104522.ris

Full Text

ELECTRON MICROSCOPIC STUDIES OF ANTENNAL SENSILLA IN THE AMBROSIA BEETLE TRYPODENDRON LINEATUM (OLIVIER) (SCOLYTIDAE) by HENRY A. MOECK : B. Sc., U n i v e r s i t y of B r i t i s h Columbia, 196b A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science i n the Department of Zoology We accept t h i s t hesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May* 196? In p r e s e n t i n g 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 o f the r e q u i r e m e n t s f o r an advanced deg ree a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I ag r ee t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r ag ree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Depar tment o r by h i s r e p r e s e n t a t i v e s , I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l no t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Depar tment o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, Canada i i ABSTRACT The antennae of the ambrosia beetle Trypodendron lineatum ( O l i v i e r ) were examined with the l i g h t and el e c t r o n microscopes to determine the types, d i s t r i b u t i o n , and structure of sense organs found thereon. At l e a s t s i x types of sense organs were found, with an a d d i t i o n a l seventh c u t i c u l a r structure, the hypodermal gland pore, which i s thought to be non-sensory. The s e n s i l l a are s e n s i l l a chaetica, three types of sensillum t r i -choideum, s e n s i l l a basiconica, and s e n s i l l a campaniformia. D i s t r i b u t i o n maps of the various sensillum types and the gland pores are presented, f o r one each of female and male l e f t antenna. S e n s i l l a chaetica, evenly d i s t r i b u t e d over a l l parts of the antennae, as w e l l as the r e s t of the body, consist of a long thick-walled h a i r 20 to ll|0 micra long which a r t i c u l a t e s i n a socket composed of a h a i r root, socket l i n i n g , and spongy cylinder. A s i n g l e b i p o l a r neuron terminates i n a scolo-pale attached at one side of the h a i r base. S e n s i l l a t r i c h o i d e a , Type I, situated at the base of the scape and the base of the f i r s t f u n i c u l a r segment, are short t h i n hairs a r t i c u l a t i n g i n a socket. Their f i n e structure and innervation are not known. S e n s i l l a t r i c h o i d e a , Type I I , found on the d i s t a l periphery of the club only, consist of sharply pointed smooth hairs 18 to 25 micra long, the h a i r wall being t h i n and perforated. The h a i r i s s o l i d l y joined to the body c u t i c l e . The sensillum has two b i p o l a r neurons, the dendrites of which ex-tend, with s l i g h t branching, to the d i s t a l l i m i t s of the h a i r lumen. No den-d r i t i c endings could be demonstrated at the ha i r perforations. S e n s i l l a t r i c h o i d e a , Type TIT, nre evenly d i s t r i b u t e d over the d i s t a l h a l f of the a n t e r i o r club surface. The h a i r i s 26 to 36 micra long, blunt-tipped, and curved i n reverse, with the r e s u l t that the hairs protrude at r i g h t angles to the club surface and beyond a l l other v e s t i t u r e . The ha i r i i i a r t i c u l a t e s i n a socket, and has a double lumen. The dendrites o f four t o seven b i p o l a r neurons extend through the eccentric small lumen to the h a i r t i p , where, presumably, they are open to the a i r . S e n s i l l a basiconica cover both club surfaces. At l e a s t two types e x i s t , one group being short pegs 6 to 8 micra long, and another group being longer pegs or hairs l l j t o 18 micra long. The long s e n s i l l a basiconica have a t h i n perforated h a i r w a l l , the openings being slit-shaped (700A* by 100 t o 200?). The two nerve c e l l s of t h i s sensillura send two d i s t a l processes i n t o the h a i r where subsequent repeated branching occurs. The r e l a t i o n s h i p of the dendrite branches to the h a i r perforations i s not clear. S e n s i l l a campaniformia are found i n small numbers on a l l parts o f the antennae, as w e l l as other parts of the body. They consist of a short t h i n canal leading from the outside, to a sub-surface dome 3 micra i n diameter, i n the centre of which l i e s the nerve ending s i m i l a r i n appearance to the scolo-pale and nerve of the sensillum chaeticum. Also, a cross section of the antennal nerve i n the proximal portion of the scape revealed about 2100 axons. A count of the s e n s i l l a , corrected f o r the number of sense c e l l s present per sensillum, gave expected axon numbers of 18JJ5 and 1921 f o r female and male antennae, r e s p e c t i v e l y , with Johnston's organ not accounted for. Since more axons than expected are present, axon f u s i o n i s considered u n l i k e l y . This sudy may serve as the basis f o r further e l e c t r o p h y s i o l o g i c a l work to determine the functions of the various sense organs. i v , TABLE OF CONTENTS Page TITLE PAGE i ABSTRACT ' i i TABLE OF CONTENTS . i v TABLES v i FIGURES v i i ACKNOWLEDGMENTS x 1 1 1 INTRODUCTION 1 MATERIALS AND METHODS 3 1. The Insect 3 2. Methods 6 RESULTS 8 1. Sensilla Chaetica 8 2. Sensilla Trichoidea, Type I . 31 3 . Sensilla Trichoidea, Type II 35" h. Sensilla Trichoidea, Type I I I ^2 5". Sensilla Basiconica „ 51 6. Sensilla Campaniformia . . . . . . . 65 7. Axon Fusion 65 DISCUSSION . . . . . . . . 7 b 7 ) 1. General 1 u 2. Sensilla Chaetica . 75 3 . Sensilla Trichoidea, Type I 77 In Sensilla Trichoidea, Type II 77 5. Sensilla Trichoidea, Type III • • 78 6. Sensilla Basiconica 79 7. Sensilla Campanif ormia • • 80 V Page 8. Axon Fusion -81 SUMMARY AND CONCLUSIONS 82 REFERENCES 8 1 j TABLES Number Title Page I Sensillum count on T. lineatum female antenna (Figs. 5,6) . . . 73 II Sensillum count on T. lineatum male antenna (Figs. 3,M . . . . 73 v i i FIGURES Number T i t l e Page 1 Photomicrograph of Trypodendron lineatum male l e f t antenna, a n t e r i o r surface ii 2 Photomicrograph of Trypodendron lineatum two female l e f t antennae (at l e f t , p o s t e r i o r surface, at r i g h t , a n t erior surface). 5 3 D i s t r i b u t i o n map of a l l s e n s i l l a and hypodermal gland pores on male l e f t antenna, po s t e r i o r surface. 9 Ii D i s t r i b u t i o n map of a l l s e n s i l l a and hypodermal gland pores on male l e f t antenna, a n t e r i o r surface. 10 5 D i s t r i b u t i o n map of a l l s e n s i l l a and hypodermal gland pores on female l e f t antenna, posterior surface 11 6 D i s t r i b u t i o n map of a l l s e n s i l l a and hypodermal gland pores on female l e f t antenna, a n t e r i o r surface. . . . . . . . . . . . 12 7 D i s t r i b u t i o n map of hypodermal gland pores and s e n s i l l a t r i c h o i d e a , Type I, on male l e f t antenna, posterior surface. . . 13 8 D i s t r i b u t i o n map of hypodermal gland pores and s e n s i l l a t r i c h o i d e a , Type I, on male l e f t antenna, anterior surface. . . l).i 9 D i s t r i b u t i o n map of hypodermal gland pores and s e n s i l l a t r i c h o i d e a , Type I, on female l e f t antenna, posterior surface. . 15 10 D i s t r i b u t i o n map of hypodermal gland pores and s e n s i l l a t r i c h o i d e a , Type I, on female l e f t antenna, anterior surface. . 16 11 Photomicrograph of hypodermal gland pore 17 12 Photomicrograph of s e n s i l l a chaetica 17 13 Photomicrograph of same antenna as i n Fig. 2, showing long s e n s i l l a chaetica on scape (arrow) which may act as proprio-ceptors f o r club p o s i t i o n i n r e l a t i o n to scape. 17 il l E l e c t r o n micrograph of hypodermal gland pore c e l l 18 15 Photomicrograph of antenna at l e f t i n Fig. 2, showing s e n s i l l a chaetica and long s e n s i l l a basiconica 19 16 D i s t r i b u t i o n map of s e n s i l l a chaetica on male l e f t antenna, po s t e r i o r surface 21 17 D i s t r i b u t i o n map of s e n s i l l a chaetica on male l e f t antenna, a n t e r i o r surface 22 18 D i s t r i b u t i o n map of s e n s i l l a chaetica on female l e f t antenna, pos t e r i o r surface 23 v i i i Number Title Page 19 Distribution map of sensilla chaetica on female left antenna, anterior surface 2 l i 2 0 Schematic diagram of sensillum chaeticum, to scale 2 5 21 Schematic diagram of sensillum chaeticum, ciliary region, with cross sections at levels indicated 2 5 2 2 Schematic diagram of sensillum chaeticum, socket region 2 6 23 Electron micrograph of sensillum chaeticum, cross section just distal to hair base 29 2li Electron micrograph of sensillum chaeticum, longitudinal section in socket region 29 25 Electron micrograph of sensillum chaeticum, longitudinal section through tubular body 2 9 26 Electron micrograph of sensillum chaeticum, cross section through tubular body 3 0 27 Electron micrograph of sensillum chaeticum, cross section through tubular body. . 3 0 28 Electron micrograph of sensillum chaeticum, cross section of tubular body 3 0 29 Electron micrograph of sensillum chaeticum, cross section of tubular body. 3 0 3 0 Electron micrograph of sensillum chaeticum, longitudinal section of cellular components. . 3 2 3 1 Electron micrograph of sensillum chaeticum, cross section through inner segment of dendrite at the level of the centriole. 3 2 3 2 Electron micrograph of sensillum chaeticum, cross section of outer segment of dendrite 3 2 3 3 Electron micrograph of typical sensory neuron cell body and axon. 3 3 3I4 Photomicrograph of sensillum trichoideum, Type I, on first funicular segment 3h 3 5 Photomicrograph of sensillum trichoideum, Type I, on proximal bulb of scape 3h 3 6 Distribution map of sensilla trichoidea, Type II, on male left antenna, posterior surface 3 6 3 7 Distribution map of sensilla trichoidea, Type II, on male left antenna, anterior surface. . . . . . . . 3 7 ix Number Title Page 38 Distribution map of sensilla trichoidea, Type II, on female left antenna, posterior surface. . . . . . . 38 39 Distribution map of sensilla trichoidea, Type II, on female left antenna, anterior surface. . 39 . ho Photomicrograph of distal edge of club, showing Types II and III s e n s i l l a trichoidea. bO 1)1 Photomicrograph of distal edge of club, showing Types I I and III sensilla trichoidea bo ii2 Electron micrograph of sensillum trichoideum, Type II, cross section near hair base bO b3 Electron micrograph of same hair as in Fig. Ii2, cross section near tip. . . ' bO hh Schematic diagram of sensillum trichoideum, Type II, with cross sections at levels indicated ).il b5 Distribution map of sensillum trichoideum, Type III, on male left antenna, posterior surface. . . b3 b6 Distribution map of sensillum trichoideum, Type I I I , on male left antenna, anterior surface hh hi Distribution map of sensilla trichoidea, Type III, on female left antenna, posterior surface. b5 L18 Distribution map of sensilla trichoidea, Type III, on female left antenna, anterior surface h6 h9 Photomicrograph of sensillum trichoideum, Type III Ii? 50 Electron micrograph of sensillum trichoideum, Type III, cross section near tip, showing four dendrites, fluted hair wall. . . hi 51 Electron micrograph of sensillum trichoideum, Type III, oblique section showing twolumina, : six dendrites. . . . . . . . . . b7 52 Electron micrograph of sensillum trichoideum, Type III, cross section showing two lumina, seven dendrites. hi $3 Electron micrograph of sensillum trichoideum, Type III, cross section through pore canal showing cuticular sheath containing six dendrites. b8 5b Electron micrograph of sensillum trichoideum, Type III, cross section just proximal to pore canal, showing five, possibly six dendrites b8 55 Electron micrograph of sensillum trichoideum, Tyoe III, cross section just distal to ciliary regions of dendrites, showing five dendrites b8 X Number T i t l e Page 56 Electron micrograph of sensillum trichoideum, Type I I I , l o n g i t u d i n a l s e c t i o n showing inner segment, c i l i a r y r o o t l e t apparatus, and portion of c i l i a r y segment Ii9 57 Electron micrograph of sensillum trichoideum, Type I I I , s l i g h t l y oblioue s e c t i o n through outer segments of dendrites, showing microtubules h9 58 Schematic diagram of sensillum trichoideum, Type I I I , with cross sections of h a i r at l e v e l s indicated. . . . . . $0 59 Schematic diagram of sensillum trichoideum, Type I I I , cross section at l e v e l indicated i n Fig.58. . 5 0 60 D i s t r i b u t i o n map of s e n s i l l a basiconica on male l e f t antenna, posterior surface . . 5 2 . 61 D i s t r i b u t i o n map of s e n s i l l a basiconica on male l e f t antenna, a n t e r i o r surface 5 3 62 D i s t r i b u t i o n map of s e n s i l l a basiconica on female l e f t antenna, p o s t e r i o r surface. 51 63 D i s t r i b u t i o n map of s e n s i l l a basiconica on female l e f t antenna, a n t e r i o r surface 55 6h . Photomicrograph of long s e n s i l l a basiconica and s e n s i l l a chaetica 57 65 Photomicrograph of short (s) and long ( l ) s e n s i l l a basiconica. 57 66 Electron micrograph of sensillum basiconicum, surface view of sectioned unstained unfixed dried h a i r 57 67 E l e c t r o n micrograph of sensillum basiconicum, oblique section of h a i r showing dendrite branches, h a i r perforations. . 58 68 Electron micrograph of sensillum basiconicum, cross section of h a i r showing numerous h a i r wall perforations and dendrite branches i n h a i r lumen 58 69 Electron micrograph of sensillum basiconicum, oblioue s e c t i o n of h a i r showing fine filaments extending part-way i n t o the h a i r perforations. 58 70 Electron micrograph of sensillum basiconicum, cross s e c t i o n of portion of h a i r wall, showing three dark bodies with f i n e f i n g e r - l i k e projections i n wall perforations 58 71 Electron micrograph of s e n s i l l a basiconica, oblique s e c t i o n through c e l l u l a r components 59 72 Electron micrograph of sensillum basiconicum, cross section i n region of pore canal. . 59 xi Number Title Page 73 Electron micrograph of sensillum basiconicum, longitudinal section 59 7li Electron micrograph of sensillum basiconicum, cross section of outer segments of dendrites, showing single and paired tubules 61 . 75 Electron micrograph of sensillum basiconicum, cross section of ciliary region of one of two dendrites, showing 9 peri-pheral tubule pairs, absence of a central pair 61 76 Electron micrograph of sensillum basiconicum, cross section through inner, segments of dendrites at level of centrioles. . . 61 77 Electron micrograph of sensillum basiconicum, cross section through inner segments of dendrites proximal to centrioles. . . 62 78 Electron micrograph of nerve cell body. . . . . . . 63 79 Schematic diagram of sensillum basiconicum, with cross section of hair at level indicated 61 80 Schematic diagram of sensillum basiconicum, cross section at level indicated in Fig. 79 6h. 81 Distribution map of sensilla campaniformia on male left antenna, posterior surface 66 82 Distribution map of sensilla campaniformia on male left antenna, anterior surface 67 83 Distribution map of sensilla campaniformia on female left antenna, posterior surface 68 8I1 Distribution map of sensilla campaniformia on female left antenna, anterior surface 69 85 Photomicrograph of sensillum campaniforme. 70 86 Electron micrograph of sensillum campaniforme, oblique section through tubular body and dome 70 87 Schematic diagram of hypodermal gland pore 71 88 Schematic diagram of sensillum campaniforme 71 89 Electron micrograph of antennal nerve, cross section at proximal portion of scape. . 72 SYMBOLS AND ABBREVIATIONS sensilla chaetica X sensilla trichoidea, Type I • sensilla trichoidea, Type II X sensilla trichoidea, Type III o sensilla basiconica • sensilla campaniformia • hypodermal gland pores AX axon H L B body cuticle H P BM basement membrane H R C centriole H W C E cytoplasmic extensions I s C L central lumen L L C R ciliary rootlet MI C S ciliary segment of dendrite MT CU S cuticular sheath MV D dendrite NL D B dendrite branch NU DO dome 0 s DS desmosome P E' B elliptical body s E C epidermal cell s c EP epicuticle S L E R endoplasmic reticulum SM L EX exocuticle S N EX CA external canal T B G Golgi body TO C G C glial cell TO V GL C gland cell TR C GL C V gland cell vacuole TR V H hair U M HE hemocoele hair lumen hair perforation hair root hair wall inner segment of dendrite large lumen mitochondrion microtubule microvilli nucleolus nucleus outer segment of dendrite pore canal scolopale sponge-like cavity socket lining small lumen sensory neuron tubular body tormogen cell tormogen vacuole trichogen cell trichogen vacuole unit membrane x i i i ACKNOWLEDGMENTS The author wishes to express his gratitude to Dr. Kenneth Graham, Professor of Forest Entomology at the University of British Columbia, for suggesting the topic, and for providing much-needed advice and encouragement during the course of t h i s study, I also wish to thank the other members of my committee, Drs. G.G.E. Scudder and A.B.Acton, for their interest in the work, and the many helpful suggestions for the preparation of the manuscript. Special thanks are extended to Mr. Leslie Veto, Electron Microscope Technician, for teaching me the electron microscopic and associated tech-niques, and for providing helpful hints and encouragement throughout the study period. Acknowledgment is made to the University of British Columbia for providing study space and laboratory equipment, and especially for permitting the use of the electron microscopes and ultramicrotomes. This study was supported in part by the National Research Council of Canada, i n the form of a Research Grant to Dr. K. Graham; to the Council I extend my thanks. INTRODUCTION The sensilla of insects have been objects of interest and study by entomologists for a long time. Knowledge of the sensory equipment of insects is of interest to the insect anatomist, and to the behaviourist who wishes to investigate the sites and kinds of specific behavioural res-ponses. The ambrosia beetle Trypodendron lineatum*(Olivier) has been a specific object of behaviour studies in recent years (see references). These studies have been of a gross nature on the entire organism,, conduc-ted in the absence of detailed knowledge of the physical nature of the sen-sory equipment involved. Heretofore our knowledge of insect sensilla has been based mainly on studies utilizing conventional histological methods and optical microscopes. Due to the relatively low resolving power of the light microscope, and the . extremely small dimensions of sensilla and their components, a precise un-derstanding of their structure was uncertain, giving rise to much specula-tion, discussion, and debate among entomologists. The. application of the electron microscope, with its superior resolving power, to biological speci-mens in the past decade has settled many arguments regarding sense organ structure and possible function, provided more precise definition of prob-lems which could be investigated with other methods, particularly electro-physiological, and either confirmed or refuted findings based on light microscopy. It is known from various kinds of evidence that the antennae of insects, as well as other arthropods, are the site of various types of sensilla (for a recent review on insect antennae, see Schneider, 196Li). Accordingly, 'Synonyms: Xyloterus lineatus (Erichson) in Europe; and T, bivittatum (Kirby), T. cavifrons (Mannerheim), T. vittiger (Eichhoff), T. boreaiis "(Swaine). 21 attention i n the present study was directed toward antennal sense organs, p a r t i c u l a r l y those of the club region (Fig.1), because the work of Borden and Wood (1966) on Ips confusus, another s c o l y t i d beetle, based on conven- . t i o n a l microscopic techniques, ablation-behavior and covering-behaviour stu-dies, as w e l l as some preliminary electrophysiological work (Borden, 1966, 1967) indicated that t h i s region i n Scolytidae i s the s i t e of a number of di f f e r e n t s e n s i l l a mediating several behavioural responses, p a r t i c u l a r l y to s p e c i f i c odorous chemicals.i In T. lineatum i t has been established that adults of both sexes are attracted to a suitable host tree by primary attrac-tants produced i n the wood, and that beetles deprived of t h e i r antennae f a i l to respond to a t t r a c t i v e wood odours (Graham and Werner, 1956). The pur-pose of the present study i s to furnish a description of the types, d i s t r i -bution, and structure of sense organs situated on the antennae of T. l i n e a -tum, as a basis f o r further work on t h i s and related species. MATERIALS AND METHODS 1. The Insect The two-striped ambrosia beetle Trypodendron lineatum (Olivier) is a species of the family Scolytidae. The adults are of a dark brown to black coloration, with alternating dark and light longitudinal stripes on the elytra. Adult length varies between 3 and 3.5 millimeters. They are bisexu-al, and therefore i t may be presumed that while a l l individuals posses certain sensory equipment characteristic of the species, they may also possess other sensory equipment peculiar to one sex which searches for mates. It was necessary therefore to identify the sex of each individual studied. Since the sexes are conspicuously dimorphic, the task of distinguishing them is easy. The female pronotum appears rounded anteriorly as seen from above, and the front of the head is rounded, whereas in the male the pro-notum appears sraight anteriorly, and the front of the head is deeply ex-cavated (hence the synonym T. cavifrons). The antennae (Figs. 1,2), which were chosen as the specific region for this study, are composed of three regions, namely an elongated basal segment, the scape (0.31 to 0,3h mm long by 0.10 mm at widest point), a series of four very short segments, the funicle (0.13 to 0.1$ mm total length by 0.07 mm at widest point) and a terminal, flattened club of oval form (0.28 to 0.31 mm long by 0.18 to 0.20 mm at widest point). Additionally, the sex of the specimen can be identified from the shape of the antennal club under the light microscope, the male's having a narrower and more elongate proximal portion than the female's, which appears more oval in form (compare Figures 1 and 2). The base of the scape articulates with the head, and the base of the Figure 1. Photomicrograph of Trypodendron lineatum male l e f t antenna, anterior surface. Compare club shape to that of female (Fig. 2). D i s t i l l e d water mount. p i g . 2 Figure 2. Photomicrograph of Trypodendron lineatum female left antennae, (at left, posterior surface, at right, anterior surface). Note greater density of sensilla on anterior club surface. Distilled water mount. f i r s t funicular segment articulates, by membrane only, with the distal por-tion of the scape; both joints are provided with muscles. 2. Methods Adult beetles were removed from galleries in logs and stored in the refrigerator at L degrees G until used. Whole mounts of antennae were made from dead dry beetles, as well as from fresh. Light microscopy Whole mounts of unstained antennae were made in distilled water (Refrac-tive index 1.33), Permount (R.I. 1.53), and' Hyrax' (R. I. 1. 63)> between cover slips to permit observation of both surfaces. Sections were made from Epon-embedded material, prepared as below, and stained with methylene blue (1% in 1% aqueous borax solution) (Richardson et al, I960). Maps and other drawings were made with the aid of an eyepiece grid. Electron microscopy (a) Antennae from live beetles were fixed for two hours in phosphate-buffered $% glutaraldehyde (Sabatini et a l , 1963), washed in buffer, post-fixed in 1% OsOjj, washed, dehydrated in the ethanol series, followed by propylene oxide, and embedded in Epon 812 (Luft, 1961; Kay, 1965). Sections were cut on glass knives on the Sorvall Porter-Blum MT-1 ultramicrotome, mounted on carbon-collodion and carbon coated copper grids (Molenaar and Schotanus, 1962), stained with lead citrate, and examined in the Hitachi HS-7S and HU-11A Electron Microscopes, at accelerating voltages of 50.KV for the former, and 50 and 75 KV for the latter. (b) Antennae were fixed for two hours in phosphate-buffered i f * OsOjj, washed in buffer, dehydrated with 153!, then h0% ethanol, stained for one hour in 1% phosphotungstic acid (PTA) in 70$ ethanol, washed in 0.01% NaOH in 9$% ethanol (modified from Kay, 1965), dehydrated to completion in absolute ethanol, stained for two hours in saturated lead acetate in alcohol: acetone as 1:1, washed in alcohol-acetone (Kushida, 1966), followed by propylene oxide, and embedded in Epon. Sections were cut and mounted as before, and examined without further staining. (c) For correlating light microscope observations with the electron microscope, thick sections (5 to 10 u) were cut on the ultramicrotome from blocks prepared by method (a), and examined with the light microscope; areas containing known sense organ(s) were then cut out with a micro-scalpel, and the section pieces embedded, with the desired orientation, in the thermo-plastic chlorinated polyphenol resin Aroclor hh6$* with the aid of an elec-trically heated minutennadel. Thin sections were then cut, stained, and examined with the electron microscope as before. * Organic Chemicals Division, Monsanto Chemical Company, St. Louis, Mo. 8 RESULTS With the light microscope one can distinguish six main types of cuticu-lar sense organs on the antennae of both sexes of T. lineatum. Using the terminology of Snodgrass (1926), they are, respectively, sensilla chaetica (Fig.15), three types of sensillum trichoideum, sensilla basiconica (Fig. 1 5 ) , and sensilla campaniformia (Fig. 85) . The main distinguishing features of the trichoid sensilla are as follows: the Type I sensilla are short (b;i to P/O hairs situated at the base of the scape and the base of the first funicular segment; no other sensilla are present in these regions (Figs.3b,35). The other two types are only on the club, the Type II sensilla being 18/1 to 25M t long, thinwalled, and sharply pointed, whereas the TypeIII sensilla are 26/i to 36M long, thicker-walled, and blunt-tipped (Figs. bO,bl). A seventh recognizable cuticular structure, the hypodermal gland pore (Mclndoo, 1926) , distributed over most parts of the body, including the antennae, is believed to be non-sensory, and will not be referred to further (Figs. 3 to 1 1 , 1b ,87) . The following descriptions are based on evidence obtained with both the light and electron microscopes, 1. Sensilla Chaetica The sensilla chaetica are distributed over most of the body as well as the antennae (Figs.16-19), and consist of a long stiff(hair^nair set in a socket, with formative cells, and a sensory bipolar neuron which terminates at the base of the hair (Fig.20). The hair may be from I8;i to lbO;u long, the majority of hairs being about bO;a long. The longest ones are on the mid-distal portion of the scape in such a position that when the club and funicle are bent back along the scape they come in contact with these long hairs (Fig. 13). Each hair is gently curved, with many small pointed projections, and tapers to a very fine point 9 Figure 3. Distribution map of a l l sensilla and hypodermal gland, pores on male left antenna, posterior surface. 10 Figure I4. Distribution map of a l l sensilla and hypodermal gland pores on male left antenna, anterior surface. Figure 6. Distribution map of a l l sensilla and hypodermal gland pores on female left antenna, anterior surface. 13 Figure 8. Distribution map of hypodermal gland pores and sensilla trichoi-dea, Type I, on male left antenna, anterior surface. 15 Figure 9. Distribution map of hypodermal gland pores and sensilla trichoi-dea, Type I, on female left antenna, posterior surface. 16 Figure 10. Distribution map of hypodermal gland pores and sensilla trichoi-dea, Type I, on female left antenna, anterior surface. Figure 11. Photomicrograph of hypodermal gland pore. 'Permount' mount. Figure 12. Photomicrograph of sensilla chaetica. Note sharp long points, pointed projections along hairs. Distilled water mount. Figure 13. Photomicrograph of same antenna as in Fig£2j showing long sensilla chaetica on scape (arrow) which may act as proprio-ceptors for club position in relation to scape. Figure lli. Electron micrograph of hypodermal gland pore cell. Figure 1$. Photomicrograph of antenna at left in Fig. 2, showing sensilla chaetica and long sensilla basiconica. Note thick hair wall, small central lumen in sensilla chaetica, and thin wall of sensilla basiconica. 20 (Fig.12). The hair appears circular and solid in cross section, save for a small empty central lumen (Fig, 23). The hair base and socket are of a complex structure, with the following features (Fig.22): the proximal portion of the hair is attached to the body cuticle by a conical ring of longitudinally ribbed cuticle (hair root) which stains like articulating membrane, as for example that between the scape and first funicular segment. In a hair of 1 M diameter near the base the cone has a diameter of 1.8M at point of hair attachment, 2.5M at widest point of body-cuticle attachment, and a wall thickness of 0.hp. to 0.5M. Total height of the cone is about 1. fyi. The socket lining is cylindrical proximally, flaring outwards distally. It is composed of a similarly staining, though more homogeneous cuticular material, and has a wall thickness of 0.15/1. It partly bends inwards at the. point of hair attachment just distal to the hair root, thus forming a slightly wider groove around the hair base. The socket lining and the distal half of the hair root are surrounded by a sponge-like cavity which seems to be filled with air, and does not communicate with the external and internal environments (during specimen preparation nothing penetrates into this cavity)(Fig. 26). The maximum diameter of about 2M of the cavity occurs where the socket lining and distal portion of the hair root join. There is a ring-like constriction of the body cuticle just proximal to the base of the hair root. In a hair of the above dimensions the base of the socket lies approximately h.5M below the external cuticular surface. The length of the pore canal leading from the base of the hair towards the interior deoends upon the cuticle thickness at that ooint. Indeed, i f the cuticle is very thin, i t shows a thickening interiorly in the immediate vicinity of the sensillum. In the sensillum described above the cuticle is 5. 5/1 thick at the sensillum and only 3. 5M thick 6/i away. The cellular component of the sensillum consists of the following: a 21 22 Figure 17. Distribution map of sensilla chaetica on male left antenna, anterior surface 23 Figure 19. Distribution map of sensilla chaetica on female left antenna, anterior surface. Figure 20. Schematic diagram of sensillum chaeticum, to scale. Figure 21. Schematic diagram of sensillum chaeticum, ciliary region, with cross sections at levels indicated. Figure 22. Schematic diagram of sensillum chaeticum, socket region. 2 7 tormogen or socket-secreting c e l l (also called a cap c e l l ) , a trichogen or hair-secreting c e l l (enveloping c e l l ) , a single bipolar neuron, and i t s associated g l i a l c e l l ( F i g s . 2 0 , 3 0 ) . The tormogen c e l l has an elongate shape, forming a sheath around the trichogen c e l l and the dendrite, and extending as a thin lining of the sen-sillum canal to the constricting cuticular ring at the base of the socket. Fine cytoplasmic v i l l i f o r m processes extend into an extracellular vacuole (tormogen vacuole) which surrounds the d i s t a l portions of the trichogen c e l l and nerve process, and extends from the base of the hair to about 1.5M to 2M proximal to the inner surface of the cuticle. Endoplasmic reticulum, smooth or rough, appears to be largely absent, whereas wel]\formed mitochondria of an ovoid shape ( 0 . 6M by 0 . 9 M ) are abundant. A few microtubules are present i n the homogeneous cytoplasm. . The c e l l nucleus, with i t s darkly staining central nucleolus, i s variously situated, apparently depending on space considerations within the club, but i s often found just proximal to the above-mentioned vacuole. Maximum c e l l dimensions are about Sp. by I Q M . The trichogen c e l l i s even more elongate, extending from the proxi-mal portion of the nerve c e l l body to the base of the hair, a distance of 2QM or more. It forms a thin (<""».3M) sheath around the neuron except around a small portion of the c i l i a r y process, where a small flask-shaped extra-cellular vacuole (trichogen vacuole) i s found. This i s a constant feature i n this sensillum, but of unknown significance. The di s t a l portion of the trichogen c e l l i n the tormogen vacuole just beneath the hair base i s exten-ded into concentric incomplete lamellae which are about 600A thick (Fig. 2 7 ) . Desmosomes joining the c e l l membrane to overlapping parts of i t s e l f or to neural membrane are present. Endoplasmic reticulum i s sparse, and mitochon-dria are small and few. Microtubules again are present and longitudinally oriented. 28 The bipolar neuron is attached at its distal end to the base of the hair by means of a darkly staining cuticular sheath or scolopale which ter-minates distally in a short (0.3)x to 0. lui) strand of cuticle continuous with the cuticle at the point of juncture of hair base and hair root (Figs,2h,25). The point of attachment is oonstant, being in the plane of ourvature of the hair, and on the outside curve. The scolopale is bullet-shaped, pointed dis-tally, about 0.6/1 in diameter, 3/i long, and with a maximum wall thickness of IjOOA, which decreases proximally and disappears. The scolopale is surrounded by a 0.13/i thick lightly staining area which in turn is surrounded by cuti-cular strands extending to the hair base (Fig. 27). Fine radially arranged strands connect the outer strand layer with the scolopale. Within the scolopale the nerve ending is separated from i t by a clear extracellular layer 75^ thick.- The unit membrane is separated from struc-tures internal to i t by another clear layer about 20oS thick (Fig. 27). The distal X)i portion of the nerve process contains a darkly staining mass (tubular body) which at higher magnification has a mottled appearance, and shows uniform curved striation both in longitudinal and in cross section, reminiscent of protein crystals (Figs. 2b,28). The periodicity of 130A* to l 5 0 l is unrelated to microtubule diameter (200A* to 2^0%). Microtubules are abundant, and a l l are longitudinally oriented in the more proximal portion of the outer segment (Figs.-21,32), gradually decreasing in number proximally until in the region of the trichogen vacuole the dendrite has the appearance of a cilium in cross section, that is, nine double peripheral strands (lack-ing, however, the two central single ones) bounded by the cell membrane. This ciliary segment is about 1.5/i long, and 0. 21/i to 0. 26>i in diameter, with the base situated about 6u to lO/i from the tip of the scolopale, depending on canal length. A ciliary rootlet apparatus is found at the tip of the inner segment of the dendrite, and consists of a dense cup-shaped region of Figure 23. Electron micrograph of sensillum chaeticum, cross s e c t i o n j u s t d i s t a l to h a i r base. Hair socket was broken open during specimen preparation. Note small empty h a i r lumen, t h i c k h a i r wall s t a i n i n g l i k e surrounding body exocuticle, and dark-l y s t a i n i n g socket l i n i n g . OsO^ f i x a t i o n , PTA and lead acetate block s t a i n . Figure 2h. E l e c t r o n micrograph of sensillum chaeticum l o n g i t u d i n a l s e c t i o n i n socket region. Note tubular body, attachment of scolopale to h a i r base. Glutaraldehyde-osmium f i x a t i o n , lead c i t r a t e s e c t i o n s t a i n . Figure 2$. E l e c t r o n micrograph of sensillum chaeticum, l o n g i t u d i n a l s e c t i o n through tubular body. Osmium f i x a t i o n , PTA and lead acetate block s t a i n . Figure 26. Electron micrograph of sensillum chaeticum, cross section through tubular body. Osmium fixation, PTA and lead acetate block stain. Figure 27. Electron micrograph of sensillum chaeticum, cross section through tubular body. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 28. Electron micrograph of sensillum chaeticum, cross section of tubular body. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 29. Electron micrograph of sensillum chaeticum, cross section of tubular body. Osmium fixation, PTA and lead acetate block stain. 31 0.15/1 diameter from the proximal base of which emerge nine solid fibres which pass on the outside of the centriole and continue proximally as the ciliary rootlets which appear collagen-like, being banded at 130% intervals (Fig.30). The centriole, situated 0.15)i below the basal cup, is a hollow cylinder 0 .25/1 long and 0. l6 / i in diameter (Fig. 31) . The inner segment, which is 0.3JM in diameter, contains some smooth endoplasmic reticulum, microtubules, and occasionally mitochondria. The nerve cell body is elongate, about Sp in diameter, with a compara-tively large oval nucleus (Fig.33). Endoplasmic reticulum is sparse, but the Golgi complex is very prominent. Mitochondria and microtubules are re-latively abundant. An interesting structure is found in most neurons near the axonal process: i t is spherical, 0. 8/i to "Lp in diameter, and consists of a dome-shaped homogeneous mass from the surface of which emerge concen-tric lamellae 50A* thick, separated by 70A. The solid mass appears crystal-line (Fig. 3 3 ) . The axon, which proceeds without synapse to the brain, is about 0.6u to 0.8/1 in diameter, becoming thinner proximally, and contains mitochondria and microtubules along its entire length. The axon surface is coated with a dense extracellular layer which apparently is produced by the glial cells (Fig. 89). The neurones characteristically show a lighter staining than the forma-tive cells,, making their identificatin somewhat easier. 2. Sensilla Trichoidea, Type I These sensilla, which are situated at the base of the scape and the base of the f i r s t funicular segment (Figs. 7-11), are short (hp. to 8ji) thin hairs articulating in a socket (Figs. 3 l i , 3 5 ) . Little else is known of their struc-ture, since no sections of these sensilla were studied in the electron mi-o croscope. Figure 30. E l ec t ron micrograph of sens i l lum chaeticum, l ong i t ud i na l sec t i on of c e l l u l a r components. Glutaraldehyde-osmium f i x a t i o n , lead . c i t r a t e sec t i on s t a i n . F igure 31. E l e c t ron micrograph of sens i l lum chaeticum, cross sec t ion through inner segment of dendrite at the l e v e l of the c e n t r i -o l e . Glutaraldehyde-osmium f i x a t i o n , lead c i t r a t e sec t i on s t a i n . F igure 32. E l e c t r on micrograph of sens i l lum chaeticum, cross sec t ion of outer segment of dendr i te . Note abundant microtubules. Glutaraldehyde-osmium f i x a t i o n , u rany l acetate and lead c i t r a t e . s e c t i on s t a i n . 32. "A? exocuticle tormogen vacuole epidermal c e l l cytoplasmic extension tormogen c e l l mitochondrion tormogen c e l l nucleus c i l i a r y segment trichogen vacuole centriole trichogen c e l l inner segment tracheole ^ H c i l i a r y rootlet gland c e l l gland c e l l nucleus Figure 33. E l e c t r o n micrograph of t y p i c a l sensory neuron c e l l body and axon. Glutaraldehyde-osmium f i x a t i o n , lead c i t r a t e s ection s t a i n . Figure 31. Photomicrograph of sensillum trichoideum, Type I, on first funicular segment. Distilled water mount. Figure 35. Photomicrograph of sensillum trichoideum, Type I, on proximal bulb of scape. Distilled water mount. 35 3. Sensilla Trichoidea, Type II These sensilla trichoidea are found on the distal periphery of the club only, and are about four dozen in number, with most of these being on the anterior club surface (Figs. 3 6 - 3 ? ) . The hair is lo/i to 25ju long, smooth, sharply pointed distally, and hollow, with a wall thickness of 0.2/1 proxi-mally, tapering to 0.3/1 distally. The hair diameter near the base is about 1. Jj/u. The gentle curvature of the hair is in a direction opposite to that of the sensilla chaetica, but is not as pronounced as that of the Type III sensilla trichoidea described below (Figs. Ii0,ljl). The hair wall is perfora-ted, the holes appearing flask-shaped, with a narrow (200A") diameter opening to the exterior (Fig. I i3). No hair socket per se exists, the hair base being joined directly to a softer cuticular ring which tapers to a sharp line proxi-mally, and is solidly joined by its outer surface to the surrounding body cuticle. Only slight bending of the hair is thus possible. On this basis this sensillum could be called a long sensillum basiconicum. The pore canal is straight and wide, and is lined by the tormogen cell. A large tormogen vacuole is present (Fig. bb). The sensillum has two bipolar neurons, the dendritic processes of which are enclosed loosely in a cuticular sheath which extends a short way into the hair lumen (Fig . l i2) . One dendritic process is larger in diameter (0 . 25/i) than the other (0.17/i). The processes, which contain only microtubules, extend, with slight branching, to the distal limits of the hair lumen. No dendritic endings were demonstrated at the hair perforations. The appearance and limits of the remainder of the tormogen cell, as well as of the trichogen cell and the nerve cell bodies are not known, since only one sensillum of this type was successfully sectioned to slightly past the base of the hair. However, no significant differences in structure are expected from that described for sensilla chaetica. 36 Figure 36. Distribution map of sensilla trichoidea, Type II, on male left antenna, posterior surface. Figure 37. Distribution map of sensilla trichoidea, Type II, on male left antenna, anterior surface. 38 Figure 3 8 . D i s t r i b u t i o n map 6f s e n s i l l a trichoidea, Type I I , on female l e f t antenna, posterior surface. 39 Figure 39. D i s t r i b u t i o n map of s e n s i l l a t r i c h o i d e a , Type I I , on female l e f t antenna, a n t e r i o r surface. Figure hO, Photomicrograph of distal edge of club, showing Types IT and I I I sensilla trichoidea. Compare length, shape, and tips. Distilled water mount. Figure hi. Photomicrograph of distal edge of club, showing tips of Types I I and I I I sensilla trichoidea. Distilled water mount. Figure 12. Electron micrograph of sensillum trichoideum, Type I I , cross section near hair base. Note two dendrites, cuticular sheath. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure h3. Electron micrograph of same hair as in Fig. Ii2, cross section near tip. Note dendrite branches, perforated hair wall. Figure LL. Schematic diagram of sensillum trichoideum, Type I I , with cross sections at levels indicated. 0 h2 h. Sensilla Trichoidea, Type III Type III sensilla trichoidea are evenly distributed over the distal half of the anterior club surface, very few of the approximately 20 to 30 sensilla occurring on the posterior surface, and these being only on the periphery (Figs.Li5-b8). The distinctive feature of these hairs, which are 26)i to 36/1 long, is their curvature, which is quite pronounced in a direction opposite that of the sensilla chaetica, with the result that the hairs, dis-tal halves at least, protrude at right angles to the club surface, and beyond a l l other vestiture. Thus the tips of these sensilla would be the fi r s t to come in contact with any substrate the beetle encountered with its antennae (Fig.hO). These also are the only blunt sensilla, a l l others of the hair type being sharply pointed (Fig.b°). The hair exhibits longitudinal fluting which in cross section appears, as a wavy hair surface, this being more pro-nounced distally (Fig.50). An eccentric lumen with a diameter one-third that of the hair contains the nerve cell distal processes. A lighter staining central region in the proximal half of the hair contains an extracellular homogeneous material of unknown nature. The impression is thus one of a double lumen, a small one apposed to one side of the hair wall and extending into a large one which thus has a crescentic form in cross section. The hair wall is relatively thick (Fig. 52). The hair base and socket are very similar in structure to those of the sensilla chaetica, differing only in a slightly greater total socket diame-ter (3/0, the presence of a hair lumen, and a less pronounced sponge-like cavity. The pore canal also is shorter and wider. The hair.is thus probab-ly more rigid in its socket (Fig.58). The large tormogen vacuole is almost totally fi l l e d with lamellate cyto-plasmic extensions of the tormogen cell (Fig.5b). The proximal limits of the tormogen cell, as well as of the trichogen cell, are however poorly known, i Figure 1)5. Distribution map of sensilla trichoidea, Type III, on male left antenna, posterior surface. hh Fi gure h6. Distribution map of sensilla trichoidea, Type III, on male left antenna, anterior surface. Figure h7. Distribution map of sensilla trichoidea, Type III, on female left antenna, posterior surface. 16 Figure L 8 . Distribution map of sensilla trichoideaj. Type III, on female left antenna, anterior surface. Figure h9. Photomicrograph of sensillum trichoideum, Type III. Note blunt hair tip. Distilled water mount. Figure 50. Electron micrograph of sensillum trichoideum, Type III, cross section near tip, showing four dendrites, fluted hair wall. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure J>1. Electron micrograph of sensillum trichoideum, Type III, oblique section showing two lumina, six dendrites. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 52. Electron micrograph of sensillum trichoideum, Type III, cross section showing two lumina, seven dendrites. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 53. Electron micrograph of sensillum trichoideum, Type III, cross section through pore canal showing cuticular sheath containing six dendrites. Osmium fixation, PTA and lead acetate block stain. Figure Sh. Electron micrograph of sensillum trichoideum, Type III, cross section just proximal to pore canal, showing five, possibly six dendrites. Glutaraldehyde-osmium fixation, lead citrate and uranyl acetate section stain. Figure 55. Electron micrograph of sensillum trichoideum, Type III, cross. section just distal to ciliary regions of dendrites, snowing five dendrites. Osmium fixation, PTA and lead acetate block stain. Figure £6. Electron micrograph of sensillum trichoideum, Type ITT, longi-tudinal section showing inner segment, ciliary rootlet aonara-tus, and portion of ciliary segment of one dendrite. Glutar-aldehyde-osmium fixation, lead citrate section stain. Figure $1. Electron micrograph of sensillum trichoideum, Type III, slight-ly oblique section through outer segments of dendrites, schow-ing microtubules. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 58. Schematic diagram of sensillum trichoideum, Type III, with cross sections of hair at levels indicated. Figure 59. Schematic diagram of sensillum trichoideum, Type III, cross section at level indicated in Fig. 58. 51 owing to the d i f f i c u l t y of obtaining l o n g i t u d i n a l sections of the rather long (30u or more) c e l l u l a r component of the sensillum. The nervous component consists of four to seven b i p o l a r neurons (Figs. 5 0 - 5 2 ) , which send t h e i r d i s t a l processes, containing only microtubules, through the e c c e n t r i c lumen of the h a i r to the t i p , where, presumably, they are open to the a i r ; no sections of the h a i r t i p were obtained. A c u t i c u l a r sheath encloses the nerve processes from the d i s t a l parts of the inner seg-ments of the dendrites to the h a i r t i p , forming the wall of the small lumen (Figs. 5 l i , 5 5 , 5 7 ) . No pores along the h a i r w a l l are evident. The d i s t a l ends of the inner segments show exa c t l y the same c i l i a r y r o o t l e t apparatus as that described i n the sensillum chaeticum (Fig. 5 6 ) . The appearances of the inner segments, nerve c e l l bodies, and axons are also the same. The nerve c e l l bodies form a c l u s t e r which can be r e a d i l y recognized i n the sections. No nerve ending terminating at the base of the h a i r was found. 5. S e n s i l l a Basiconica S e n s i l l a basiconica occur only on the club, covering both surfaces except the corneous basal segment region (Figs. 60-63). The density of s e n s i l l a on the a n t e r i o r surface i s approximately three times that on the posterior sur-face, the t o t a l number being about 550. The length of the s e n s i l l a varies continuously between 6/i and l 8 n . However, i t i s probable that at l e a s t two types of sensillum basiconicum e x i s t . One group occurs i n small numbers on the a n t e r i o r club surface, the s e n s i l l a being short (6/i to 8/1), almost s t r a i g h t , continuously tapering to a sharp point, and having a wider pore canal (Fig. 65,s). Those of the other group covering both club surfaces are long (llni to l 8/i), c y l i n d r i c a l f o r most of t h e i r length and sharply tapering to a point, bent sharply near the base so that the sensillum l i e s p a r a l l e l to the club surface, and have a narrower pore canal (Figs.6 l i , 6 5 , 1 ) . Hair diameter i s l . t y i to 1 .6)i. The s e n s i l l a of intermediate length appear to be l e s s f u l l y 52 53 Figure 61. Distribution map of sensilla basiconica on male left antenna, anterior surface. Figure 62. Distribution map of sensilla basiconica on female left antenna, posterior surface. Figure 63. Distribution map of sensilla basiconica on female left antenna, anterior surface. 56 develloped long sensilla basiconica, although a third similar but smaller type is not excluded. Since these differences were not noted until most of the fine structure work had been done, the following description probably holds for the long basiconic sensilla, which, since they are most numerous, would be most frequently sectioned. The typical sensillum basiconicum is about 16/1 long, curved, with a non-articulated base. These sensilla are shielded from contact with a substrate by the sensilla chaetica, and the.Types II and III sensilla trichoidea. Since they come to a very sharp point, an opening at the tip is presumed absent. The hair wall is very thin, tapering from 0.22p. near the base to O.lO/i near the tip. From about 3p- from the base the hair wall shows many perforations, about 50 to 60 per square micron of surface area (Fig.66). The holes are flask-shaped, being wide internally (500A), and opening to the exterior by a narrow longitudinally oriented s l i t which is about 700A" long, and IOOK to 200A" wide. The base is not articulated, the hair wall being joined directly to the body cuticle as in the Type II sensilla trichoidea. The pore canal is simple, cylindrical, about 3p long and 1.7p in diameter (Fig. 7 9 ) . The tormogen cell again is typically disposed, forming the pore canal lining, and ensheathing proximally the trich@'gen cell. The tormogen vacuole is characteristically very large, extending from the base of the hair to hp or more proximal to the inner cuticular surface, and with a maximum diameter approaching hp. The vacuole is loosely filled with tormogen cell cytoplasmic extensions which are villiform to somewhat lamellate, and which centrally terminate \p to 2p proximal to the pore canal (Fig. 7 1 ) . The cytoplasm is -; dense, with sparse endoplasmic reticulum, and a moderate number of mito-chondria. The nucleus is usually situated proximal to the vacuole. The trichogen cell shows a characteristic specialization: a large Figure 6b. Photomicrograph of long sensilla basiconica and sensilla chaetica. Note the hint of perforations in the hair wall of the sensilla basiconica. Distilled water mount. Figure 65. Photomicrograph of short (s) and long (l) sensilla basico-nica. Compare length and peg shape. 'Permount' mount. Figure 66, Electron micrograph of sensillum basiconicum, surface view of sectioned unstained unfixed dried hair. Note slit-shaped openings. Figure 67. Electron micrograph of sensillum basiconicum, oblique section of hair showing dendrite branches, hair perforations. Glutar-aldehyde-osmium fixation, lead citrate section stain. Figure 68. Electron micrograph of sensillum basiconicum, cross section of hair showing numerous hair wall perforations and dendrite branches in the hair lumen. Note dendrite branch ending in a perforation (arrow). Figure 69. Electron micrograph of sensillum basiconicum, oblique section of hair showing fine filaments extending part-way into the hair perforations.(arrow). Osmium fixation, PTA and lead acetate block stain. Figure 70. Electron micrograph of sensillum basiconicum, cross section of portion of hair wall, showing three dark bodies with fine finger-like projections in wall perforations. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 71. Electron micrograph of sensilla basiconica, oblique section through cellular components. Osmium fixation, PTA and lead acetate block stain. Figure 72. Electron micrograph of sensillum basiconicum, cross section in region of pore canal. Note two dendrites. Osmium fixation, PTA and lead acetate block stain. Figure 73. Electron micrograph of sensillum basiconicum, longitudinal section. Glutaraldehyde-osmium fixation, lead citrate section stain. 60 trichogen vacuole, approximately 5/i long and h.Sp. in diameter, extends from 3/i proximal to the tips of the two inner segments of the dendrites of this sensillum to the tormogen vacuole, from which i t is separated by a cuticular sheath which encloses the dendritic outer segments (Figs.76,77). In this region the dendrites are completely but loosely surrounded by 5 to 7 cyto-plasmic anastomosing lamellae which originate at the proximal end of the trichogen vacuole, with occasional connections to the lateral cytoplasmic walls, giving this region a myelin-like appearance in cross section. The lamellae contain microtubules, and mitochondria which cause local swellings. Desmosomes join the inner lamellar membranes to the dendrite cell membranes, (Fig.80). Proximally the trichogen cell encloses the remaining parts of the inner segments and the nerve cell bodies. The nucleus is near the proximal part of the nerve cell bodies, 25/i to 3QM from the base of the hair. The cuticular sheath mentioned earlier is thin-walled (300A* to bOoX), 0.5/i to 0.8/i in diameter, an irregularly wavy line in longitudinal section, and extends from the distal portion of the trichogen vacuole to a short dis-tance into the hair lumen where i t flares outwards to join the hair wall (Figs.71,73). The two nerve cells of this sensillum, similar in appearance to those of the other sensilla, send two distal processes (which again are cilium-like proximally, with the ciliary rootlet apparatus, Figs.7li-77) unbranched into the hair, where subsequent repeated branching occurs. Curiously, each of the 15 to 20 branches contains at least one microtubule. Each hair per-foration contains a darkly staining body which f i l l s the small cavity, but bears no apparent connection to the nerve branches in the hair lumen (Fig. 7 0 ) . Only one hair section photographed shows a nerve branch terminating within a perforation, with several small finger-like projections about 13ol thick (Fig,68), The dark bodies also have on.their distal border finger-like Figure Ih. Electron micrograph of sensillum basiconicum, cross section of outer segments of dendrites, showing single and paired tubules. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 7?. Electron micrograph of sensillum basiconicum, cross section of ciliary region of one of two dendrites, showing 9 peripheral tubule pairs, absence of central pair. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 76. Electron micrograph of sensillum basiconicum, cross section through inner segments of dendrites at level of centrioles. Glutaraldehyde-osmium fixation, lead citrate section stain. 0 Figure 77. Electron micrograph of sensillum basiconicum, cross section through inner segments of dendrites proximal to centrioles. Note e i U a r y ?©eilets, dismeieraea, Qlutar^ifehytte-osmium fixation, lead citrate section stain. Figure 78. Electron micrograph of nerve cell body. Osmium fixation, PTA and lead acetate block stain. Figure 79. Schematic diagram of sensillum basiconicum, with cross section of hair at level indicated. Figure 80. Schematic diagram of sensillum basiconicum, cross section at level indicated in Fig. 79. tt projections, these, however, being only HJA" to 20A in diameter (Fig. 7 0 ) . This point is s t i l l unsettled, and could bear further critical examination. 6. Sensilla Campaniformia The sensilla campaniformia occur in small numbers on a l l parts of the antenna, as well as other parts of the body (Figs. 8 I - 8 I 4 ) . They consist of a short thin canal leading from the outside to a subsurface solid dome-shaped structure 3p- in diameter, into the centre of which extends the nerve ending similar in appearance to the scolopale and nerve of the sensillum chaeticum ( F i g s . 8 6 , 8 8 ) . The pore canal flares outwards distally, giving the entire structure the appearance of an icecream cone. Little else is known of the structure of these sensilla due to their infrequent appearance in sections. 7. Axon Fusion Mention can be made at this time of the attempt to determine whether fusion of sensory axons occurs in the antennae, as has been reported in other insects (Wigglesworth,1959; Dethier, Larsen, and Adams,1963). A cross section of the antennal nerve in the proximal portion of the scape of a female re-vealed approximately 2100 axons (Fig. 89). The sensillum count and expected nerve fibres in the illustrated antennae is given in Tables I and II. The total expected axons thu3 are IftbS and 1921 for female and male respectively, with Johnston's organ not accounted for. Fusion of axons is thus considered unlikely, since more axons than expected are present in the antennal nerve. 66 Figure 81. Distribution map of sensilla campaniformia on male left antenna, posterior surface. 67 68 Figure 83. Distribution map of sensilla campaniformia on female l e f t antenna, posterior, surface. 69 Figure 81j. D i s t r i b u t i o n map of s e n s i l l a campaniformia on female'left antenna, anterior surface. Figure 85. Photomicrograph of sensillum campaniforme. Distilled water mount. Figure 86. Electron micrograph of sensillum campaniforme, oblique section through tubular body and dome. Glutaraldehyde-osmium fixation, lead citrate section stain. Figure 87 . Schematic diagram of hypodermal gland pore. Figure 88 . Schematic diagram of sensillum campaniforme. 71 E X C A 1 ( Figure 89. Electron micrograph" of antennal nerve, cross section at proximal portion.ao) scape. Glutaraldehyde-osmium fixation, lead citrate and "uranyl acetate section stain. 73 Table I. Sens i l lum count on T. l ineatum female antenna (F igs . 5,6) Type of sens i l lum Number of s e n s i l l a Nerve To ta l Pos te r io r Anter io r To t a l c e l l s nerve surface surface per f i b r e s sens i l ium Sensi l lum chaeticum 192 280 L72 1 . 172 Sensi l lum tichoideum Type I 9 15 2b 1? 2b Sensi l lum tr ichoideum Type I I 8 39 17 2 9b Sensi l lum tr ichoideum Type III 3 2b 27 6 162 Sens i l lum basiconicum 126 bos 53b 2 1068 Sensi l lum campaniforme 15 10 25 1 25 Tota l s 353 776 1129 I8b5 Table I I . Sens i l lum count on T. l ineatum male antenna (Figs.3,b) Type o f sens i l l um Number of s e n s i l l a Nerve T o t a l Pos te r io r An te r io r T o t a l c e l l s nerve surface surface per f i b r e s sens i l lum Sensi l lum chaeticum 195 31b 509 1 509 Sensi l lum tr ichoideum Type I 9 20 29 1? 29 Sensi l lum tr ichoideum Type II 6 b2 1.8 2 96 Sensi l lum tr ichoideum Type I I I b 18 22 6 132 Sensi l lum basiconicum 130 b3b 56b 2 1128 Sensi l lum campaniforme 16 11 27 1' 27 Tota l s 360 839 1199 1921 7 h DISCUSSION 1. General Much of the e x i s t i n g confusion regarding insect sense organ function stems from the f a c t that sense organs, of necessity, were o r i g i n a l l y c l a s s i -f i e d according to gross morphological c h a r a c t e r i s t i c s (Snodgrass,1935). Since most of the c r i t i c a l s p e c i a l i z e d structures of the nerve endings are smaller than the r e s o l v i n g power of the l i g h t microscope, few conclusions could be drawn regarding the possible functions of sense organs. Behavioural studies, coupled with a b l a t i o n experiments could, at best, give information only on the b o d i l y l o c a t i o n of sense organs, but due to the abundance and density of various types of s e n s i l l a on, f o r example, the antennae, l i t t l e could be said regarding the sense organ(s) a c t u a l l y mediating a given beha-v i o u r a l pattern. Matters are f u r t h e r complicated by the presence of up to s i x t y sense c e l l s i n one sensillum ( S l i f e r , 1 9 6 l ) , each po s s i b l y responding to d i f f e r e n t s t i m u l i , or i n a d i f f e r e n t manner to the same s t i m u l i . Only under very favorable conditions could a function be ascribed to a given sense organ. This, however, did not mean that the ascribed function was the only one the sense organ possessed, i f more than one sense c e l l was present. For example, each of up to f i v e sense c e l l s of the l a b e l l a r h a i r s of blow-f l i e s has a d i f f e r e n t function (Hodgson,1965). Furthermore, electrophysio-l o g i c a l work has revealed q u a l i t a t i v e as well as quantitative differences i n response to the same s t i m u l i by the sense c e l l s of morphologically i n d i s t i n -guishable s e n s i l l a (Sturckow,1963; Schneider, Lacher, and Kaissling , 196M. Thus great care must be taken when attempting to make generalizations about the function of a given type of sensillum, even when f i n e - s t r u c t u r a l and e l e c t r o p h y s i o l o g i c a l evidence i s ava i l a b l e . The present study on i n s e c t s e n s i l l a has revealed several i n t e r e s t i n g features. F i r s t l y , a l l b i p o l a r neurons so f a r studied are v i r t u a l l y i n d i s -75 t ingu ishab le from each other proximal to and inc lud ing the c i l i a r y por t ion of the den t r i t e . The main d i f f e rences l i e i n the te rmina l s p e c i a l i z a t i o n of the outer segments, i . e . the manner i n which the sense c e l l i s exposed to the environment, which i s e i t he r d i r e c t l y through holes i n the c u t i c l e , or by means of a c u t i c u l a r transducer mechanism. Secondly, sense c e l l s which respond to s i m i l a r environmental modal i t ies show a s i m i l a r f i n e - s t r u c t u r a l o rgan iza t ion of the outer segments. This does not necessa r i l y apply to the Type II mu l t i dendr i t i c neurons. Comparison of the present r e s u l t s with those o f other workers us ing the e l e c t ron microscope ind ica tes that the above f e a -tures may be common to most c u t i c u l a r sense organs found i n other insec t orders (Adams and Holbert, l°63; Adams, Ho lber t , and Forgash,1965; Anonymous, 196b; Boeckh, K a i s s l i n g , and Schneider,I960; Dethier,1963; Deth ie r , Larsen, and Adams,1963; Deth ier and Wblbarsht,1956; dray, I960; Hodgson,1965; Kuwaba-ra,1963; Larsen,1962, 1963; Larsen and Dethier,1963; Noble-Nesbitt ,1963a, 1963b; Osborne,1963, 196b; Osborne and Finlayson,1965; Peters , I960; Pres-tage, S l i f e r , and Stephens,1963; Schneider,196b; Schneider, Lacher, and Ka i s s l i ng ,196b ; S l i f e r , 1 9 6 l , 1963; S l i f e r , Prestage, and Beams,1957, 1959; S l i f e r and Sekhon,196l, 1962, 1963, 196ba, 196bb, 196bc; S l i f e r , Sekhon, and Lees,196b; Thurm,196b, 1965; Uga and Kuwabara,1965). 2. S ens i l l a Chaetica . The abundant and widely d i s t r i bu t ed s e n s i l l a chaet ica are probably a l l innervated by a s ing l e neuron each. For that reason mul t ip le func t ion of a given sens i l lum can be excluded. A l so , chemical f unc t i on , as we l l as respon-ses to temperature, osmolar i ty , and C0 2 can be r e a d i l y excluded, s ince the ha i r i s th ick-wal led with an empty smal l lumen, and the sense c e l l terminates at the base of the h a i r , be ing a d d i t i o n a l l y encased by the s co lopa le , thus e f f e c t i v e l y s h i e l d i n g the neuron from s t imu la t ion by those moda l i t i es . On the other hand, the s t ruc ture o f the socket and h a i r , with the attached 76 scolopale, provides an e x c e l l e n t opportunity f o r stimulating the c e l l by a bending of the hair. Whether t h i s i s accomplished by contact with a strate,yby air-borne sound, by a i r currents, or by d i f f e r e n t i a l c u t i c u l a r absorption of water as a r e s u l t of humidity changes can at present not be resolved, but the f i r s t seems the most l i k e l y p o s s i b i l i t y . The thickness of the h a i r , r e l a t i v e shortness, curvature, and apparent s t i f f n e s s make a i r -borne sound and a i r currents u n l i k e l y s t i m u l i ; h airs which are known to respond to sound or a i r currents are u s u a l l y very long, t h i n , protruding almost at r i g h t angles to the c u t i c l e surface, and set i n a wide membrane, a l l features apparently making d e f l e c t i o n of the h a i r easier (Dethier,1963; Schwartzkopff,19610. Since the h a i r i t s e l f seems to be constructed e n t i r e l y of non-staining impermeable e x o c u t i c l e , and since no d i f f e r e n t i a l substruc-ture was noted, water absorption as a means of humidity detection i s c o n s i -dered u n l i k e l y . I f an e f f e c t does occur i n the socket only, the h a i r i t s e l f would be superfluous, and one would have to explain i t s presence as well as structure; the single sense c e l l precludes a double function. The remaining choice of function, touch reception, i s a l o g i c a l one when one considers the presence of the s e n s i l l a on a l l exposed body parts, t h e i r greater density on c r i t i c a l parts l i k e the antennae, front of the head, pronotum, legs, posterior region, and t h e i r o r i e n t a t i o n and f i n e structure. The' d i s t a l nerve process of known mechanoreceptors, the h a i r plate s e n s i l l a and campaniform s e n s i l l a of bees examined by Thurm (1963, 196ha, 196hb, 1965), contains a s p e c i a l terminal structure i n the form of a bundle of tubules designated the 'tubular body', c o n s i s t i n g of 50 to 100 tubules l y i n g p a r a l l e l to one another i n an e l e c t r o n dense material. The t o t a l diameter of each tubule i s approximately l5oX. P h y s i o l o g i c a l and morphological r e s u l t s i n d i c a t e that compression at the s i t e of t h i s body probably acts as the stimulus at the c e l l u l a r l e v e l (Thurm,196La). A s i m i l a r structure i s found i n the terminal nerve process 77 of the s e n s i l l a chaetica examined here, although the tubular nature has not ever, agrees clos e l y with the above measurement^ (^ See Fig. 29.Jj?he hair plate s e n s i l l a were found by Thurm (1965) to possess d i r e c t i o n a l s e n s i t i v i t y , t h i s being d i r e c t l y related to the point of attachment of the scolopale to the h a i r base. A s i m i l a r relationship appears to hold i n the s e n s i l l a chaetica; by comparison, a force acting on the hair from upper l e f t to lower r i g h t i n Fig. 20 would be most r e a d i l y perceived. This would be of maximal advantage to the animal, since t h i s i s the most l i k e l y d i r e c t i o n a natural stimulus would have. Electrophysiological v e r i f i c a t i o n i s of course essential. Sen-s i l l u m position may further indicate function: The long s e n s i l l a chaetica on the scape may act as proprioceptors, informing the beetle of the position of the club when the antenna i s withdrawn against the head. 3. S e n s i l l a Trichoidea, Type I Since nothing i s known of the fine structure of the Type I s e n s i l l a trichoidea, nothing can be said about the possible function on t h i s basis. However, t h e i r very l o c a l i z e d d i s t r i b u t i o n , as w e l l as t h e i r gross resem-blance to h a i r plate s e n s i l l a of other insects, suggest proprioception as a l i k e l y function. In some whole mounts of antennae the hairs on portions of the f i r s t funicular segment are v i s i b l y bent against the c u t i c l e of the scape. S i m i l a r l y , different hairs on the proximal bulb of the scape would be bent against the surrounding head capsule, depending on antennal position. Further work to determine fine structure of these s e n s i l l a i s required, h. S e n s i l l a Trichoidea, Type I I ' The most in t e r e s t i n g feature of these s e n s i l l a i s the perforated h a i r wall. Although the relationship between the nerve branches and the pores could not be c l e a r l y demonstrated, comparisons can s t i l l be drawn between these s e n s i l l a and the long t r i c h o i d s e n s i l l a of Bombyx and Antheraea been so c l e a r l y demonstrated. The 130A to 150A* p e r i o d i c i t y described, how-78 males (Boeckh, K a i s s l i n g , and Schneider,1965), and the basiconic s e n s i l l a of several insect orders, including Coleoptera (Slifer,1961, 1963; S l i f e r et a l , 1957, 1959; S l i f e r and Sekhon, 1961, 1962, 1963, 196Jja, 196iib, 1961c)s the nerve branches each contain at least one microtubule, and the number of c u t i -cular pores f a r exceeds the number of nerve branches i n the hair. Since S l i f e r and Sekhon (I96ua, 196hc) have c l e a r l y demonstrated filaments passing from the sides of the nerve branches to the pores, a sim i l a r relationship i s assumed to hold here; (_ Fig.69 indicates that t h i s i s probably the case, at least i n the s e n s i l l a basiconica. The long t r i c h o i d s e n s i l l a on the antennae of male Bombyx mori and Antheraea pernyi were examined e l e c t r o p h y s i o l o g i c a l ^ (Boeckh, K a i s s l i n g , and Schneider,1965; Schneider, Lacher, and Kai s s l i n g , 196li) and were found to respond to the respective female-produced sex attractant. No reaction was found to mechanical, thermal, CO2, or humidity s t i m u l i . The other one or two c e l l s of the s e n s i l l a trichoidea usually present did not respond to the sexual attractant but gave a phasic impulse increase or decrease to the general odour, ^ u r i p u s l y ^ t h e females, which do not respond to t h e i r own sex attractant, lack the long s e n s i l l a trichoidea. In the present case i t i s thus assumed that the Type I I s e n s i l l a trichoidea are ol f a c t o r y receptors, not excluding possible responses to temperature, humidity, and CC^. Mecha-noreception i s considered u n l i k e l y : the hair base i s not a r t i c u l a t e d , and no neuron terminates at the base. 5. Sensilla Trichoidea, Type I I I The Type I I I s e n s i l l a trichoidea hold a considerable number of features i n common with the contact chemoreceptor t r i c h o i d s e n s i l l a of many other insects. These are the reverse curvature of the h a i r , the longitudinal hair f l u t i n g , the blunt t i p , the double lumen, the eccentric small lumen apposed to one side containing the d i s t a l processes of several neurons, and the a r t i -79 culated hair base. I t i s thus very tempting to consider these s e n s i l l a as contact chemoreceptors. The position of these s e n s i l l a on the d i s t a l h a l f of the anterior club surface, as well as t h e i r exposed nature, f a c i l i t a t i n g contact with a substrate, further strengthen t h i s view. Sections of the hair t i p are s t i l l required to determine the relationship of nerve endings to the external environment; at t h i s time the presence of terminal pores i s assumed. Since a systematic study of the fine structure of each hair on a given club was not undertaken, the relationship between hair position and nerve c e l l number, and the absence or presence of a nerve c e l l terminating at the h a i r base were not determined. This would have to be done i f any attempts are made at electrophysiological recording of responses. Further-more, i t must be kept i n mind that morphological i d e n t i t y , with respect to nerve c e l l number and di s p o s i t i o n , does not necessarily mean physiological i d e n t i t y , since different combinations of c e l l s responding to various s t i m u l i may be present i n hairs of s i m i l a r appearance. Each hai r must thus be exa-mined separately, both f o r morphology and function. Speculation on the function of i n d i v i d u a l c e l l s i s pointless since t h i s insect has a highly specialized diet (ambrosia fungus), the chemical composition of which i s unknown. Contact chemoreceptor c e l l s responding to water, carbohydrates, and s a l t s were found i n Diptera (Dethier,1963); t h i s information may be used as an i n i t i a l guide. Additionally, some contact chemoreceptor s e n s i l l a were found to respond to mechanical stimulation - bending of the h a i r , t h i s being related to the presence of a nerve termination at the hai r base (Dethier 1963). 6. Sen3illa Basiconica In common with the Type I I s e n s i l l a trichoidea, the s e n s i l l a basiconica have a perforated h a i r w a l l , two neurons each, and branching of the outer segments, d i f f e r i n g only i n the greater amount of nerve branching and the greater number of hair perforations. Since t h e i r fine structures are so s i -80 milar, the sensilla basiconica are also assumed to be olfactory organs, again not excluding possible reception of viator vapor, CO2, and temperature. Due to their stoutness, lack of articulation, and protected nature, they are also considered unlikely as mechanoreceptors. The exact nature of the receptor membrane, and the relationship of pores to dendrite branches remain to be elucidated. Since no study exists in which given sensilla basiconica were examined both electron microscopically and electrophysiologically, no reaso-nable comparisons can be made using only fine structure as the basis. Fur-thermore, at least two general types of sensillum basiconicum presumed res-ponsive to odours exist: one type with perforated hair walls as described above, and another type in which the cuticular sheath containing the dendri-tes passes up the hair lumen to the tip of the hair, where the dendrite tips are exposed to the air (Slifer, Prestage, and Beams,1957, 1959). Due to the large differences in receptive surface area presented to the environment, these two types undoubtedly differ greatly in the types of chemicals to which they can respond, as well as to their concentration. Perforated hairs and pegs were found by other workers on the antennae of bees (Slifer and Sekhon, 1961), moths (Boeckh, Kaissling, and Schneider,1965), mosquitoes (Slifer and Sekhon,1962),bugs (Slifer and Sekhon,1963), flies (Slifer and Sekhon,196hb), grasshoppers (Slifer and Sekhon,196hc), and beetles (Slifer and Sekhon,196ba). The second type of sensillum basiconicum has not yet been found on the an-tennae of T. lineatum; their presence is however not excluded. 7. Sensilla Campaniformia The mechanoreceptive function of campaniform sensilla has been well es-tablished for some time (Pringle,1938a, 1938b), contrary to Mclndoo's b e l i e f that they functioned as olfactory receptors (McTndoo,19lii). More specifical-ly, the sensilla respond to stresses in the cuticle resulting from mechanical deformation (Dethier,1963). Since no significant differences in structure 81 ware found l n the s e n s i l l a of t h i s insect, compared to those of others, a s i m i l a r function i s assumed. The fine structure of the nerve ending appears almost i d e n t i c a l to that of the bee campaniform sensillum examined with the electron microscope by Thurm (196b). He concludes that compression at the s i t e of the tubular body i s the adequate stimulus at the c e l l u l a r l e v e l . 8. Axon Fusion The probable absence of sensory c e l l axon fusion i s an important finding since i t means that the function of each sense c e l l can be i n d i v i d u a l l y recor-ded i n the brain, without summation effects. Since Steinbrecht (unpublished, c i t e d i n Boeckh, K a i s s l i n g , and Schneider,1965), using the electron micros-cope, also found no evidence of axon fusion i n Bombyx antennae, and since many of the nerve f i b r e s are of a size below the resolution l i m i t of the l i g h t microscope, the s i t u a t i o n should be reinvestigated with the electron microscope i n Rhodnius and Phormia antennae, i n which extensive axon fusion supposedly ex i s t s (Wigglesworth,1959; Dethier, Larsen, and Adams,1963). 82 SUMMARY AND CONCLUSIONS . The antennae of the ambrosia beetle Trypodendron lineatum ( O l i v i e r ) were examined with the l i g h t and electron microscopes to determine the tyoes, d i s t r i b u t i o n , and structure of c u t i c u l a r sense organs found thereon. VThole mounts of antennae were used to determine types and d i s t r i b u t i o n of s e n s i l l a . Sections of Epon-embedded specimens were either stained with methylene blue and examined with the l i g h t microscope, or stained with heavy metal s a l t s and examined with the electron microscope. A b r i e f investigation was made of the presence or absence of sensory axon fusion i n the antennae. The conclusions are as follows: 1. Six main types of sense organs are present on the antennae, with an additional seventh c u t i c u l a r structure, the hypodermal gland pore, which i s thought to be non-sensory. 2. The s e n s i l l a are s e n s i l l a chaetica, s e n s i l l a trichoidea Types I, I I , and I I I , s e n s i l l a basiconica, and s e n s i l l a campaniformia. 3. Di s t r i b u t i o n maps of a l l s e n s i l l a and the hypodermal gland pores on one each of l e f t male and female antenna are presented. L. S e n s i l l a chaetica, of wide d i s t r i b u t i o n , possess one bipolar neuron terminating i n a scolopale at the base of the thick-walled articulated hair. 5. Type I s e n s i l l a trichoidea are short hairs at the base of the scape and the base of the f i r s t funicular segment. Their fine structure and innervation are not known. 6. Type I I s e n s i l l a trichoidea are Sharp-pointed hairs of intermediate length, with t h i n , perforated h a i r walls and two neurons with s l i g h t l y branched dendrites as the main features. D i s t r i b u t i o n i s r e s t r i c t e d to the d i s t a l periphery of the club. 7. Type I I I s e n s i l l a trichoidea, on the d i s t a l half of the anterior club surface, are blunt-tipped, reversely-curved hairs possessing a double 8 3 lumen and four to seven bipolar neurons, the unbranched dendrites of which extend to the hair tip. The presence of hair tip perforations is assumed. 8. Sensilla basiconica, on both club surfaces, are relatively short thin-walled perforated hairs or pegs, possessing two neurons each, with much-branched dendrites. The relationship of dendrite branches to hair perfora-tions is not clear. 9. Sensilla campaniformia, of wide distribution, consist of a sub-sur-face dome in the centre of which lies the nerve ending of one neuron similar in appearance to that of the sensilla chaetica. 1 0 . The number of antennal nerve axons exceeds the expected number of axons obtained by a sensillum count corrected for the number of nerve cells present per sensillum type, with Johnston's organ unaccounted for, indicating the probable absence of sensory axon fusion in the antennae. 11. The possible functions of the six sensillum types are discussed. 12. The implications of past research into insect sense organ function, and the value of studies such as the present one, are discussed. 8b REFERENCES (References marked with an asterisk are not specifically referred to in the Thesis). *Adams, J.R., and A.J. Forgash. 1966. The location of the contact chemore-ceptors of the stable fly. Stomoxys calcitrans (Diptera: Muscidae). Ann. Ent. Soc. Amer. 5 9 ( 1 ) : 133-lbl Adams, J.R., and P.E. Holbert. 1963. The fine structure of insect contact chemoreceptors. Proc. XVT Int. Congr. Zool. 3_: 93-95 Adams, J.R., P.E. Holbert, and A.J. Forgash. 1965. Electron microscopy of the contact chemoreceptors of the stable fly, Stomoxys calcitrans (Diptera; Muscidae). Ann. Ent. Soc. Amer. 58: 909-917 •Anderson, L.W., and H.J. Ball. 1959. Antennal hygroreceptors of the milk-weed bug Ojicop^eD^tus^ascJ^tus (Dallas) (Hemiptera, Lygaeidae). Ann. Ent. Soc. Amer. £2: 279-28L Anonymous. 196b. Photographs of labellar sensilla as studied by scanning electron microscope. Life 5 6 ( l 8 ) : 69-72 *Barber, S.B., and W.F. Hayes. 1963. Properties of Limulus chemoreceptors. Proc. XVT Int. Congr. Zool. 3 : 76-78 *Barrows, W.M. 1907. The reactions of the pomace fly, Drosophila amoelophiia Loew, to odorous substances. J. Exp. Zool. b_: 515-537 *Barton-Browne, L. I960. The role of olfaction in the stimulation of ovipo-sition in the blowfly, Phormia regina. J. Ins. Physiol. 5s 16-22 *Barton-Browne, L. 1963. Some possible modes of action of humidity and water receptors in insects. Proc. XVI Int. Congr. Zool. 3 : 86-88 *Barton-Browne, L., and E.S. Hodgson. 1962. Latency, independence and spe-ci f i c i t y of labellar chemoreceptors of the blowfly, Lucilia. J. Cell'. Comp. Physiol. 59: 187-202 *Begg, M., and Hogben, L. 19b6. Chemoreceptivity of Drosophila melanogaster. Proc. Roy. Soc. (B) 133: 1-19 *Birukow, G. 1958. Zur Funktion der Antennen beim MistkSfer (Geotrupes silva-ticus)(Panz.). Z. Tierpsychol. 15: 265-276 *Boeckh, J. 1962. Elektrophysiologische Untersuchungen an einzelnen Geruchs-rezeptoren auf der Antenne des TotengrSbers (Necrophorus). Z. Vergl. Physiol. b_6: 212-2b8 Boeckh, J., K.E. Kaissling, and D. Schneider. I960. Sensillen und Bau der Antennengeissel von Telea polyphemus. Zool. Jb. (Anat.) 78: 558-58b *Boeckh, J., K.E. Kaissling, and D. Schneider, 1965. Insect olfactory recep-tors. Cold Spring Harbor Symp. Quant. Biol. 3 0 : 263-280 85 Borden, J.H. 1966. Laboratory investigations of certain phenomena associa-ted with the resoonse of Tps confusus (LeConte) (Coleoptera: Scolyti-dae) to male attractant. Ph.D. Thesis, University of California Borden, J.H. 1967. Personal communication Borden, J.H., and D.L. Wood, 1966. The antennal receptors and olfactory response of Ips confusus (LeConte) (Coleoptera: Scolytidae) to male sex attractant in the laboratory, Ann. Ent. Soc. Amer. 59253-261 •Bullock, T.H., and G.A. Horridge. 1965. Structure and Function in the  Nervous System of Invertebrates. Freeman & Co., San Fran. 2 Vol. •Burkhardt, D. I960. Action potentials in the antennae of the blowfly (Calliphora erythrocephala) during mechanical stimulation. J. Ins. Physiol, b: 138-11J5 •Byrne, H.D., and A.L. Steinhauer. 1966. The attraction of the alfalfa weevil Hypera postica (Coleoptera: Curculionidae), to alfalfa. Ann. Ent. Soc. Amer. 59(2): 303-309 •Byrne, H.D., A.L. Steinhauer, and R.E. Menzer. 1966. Attractiveness of alfal fa extracts to the alfalfa weevil, Hypera postica, in relation to water. Ann. Ent. Soc. Amer. 59(5): 1013-loTJj •Chamberlin, W.J. 1939. The Bark and Timber Beetles of North America North  of Mexico. OSC Co-op. Assoc., Corvallis, Oregon •Chamberlin, W.J. 1958. The Scolytoidea of the Northwest, Oreppn, Washington, Idaho, and British Columbia. Oregon State College, Corvallis, Oregon •Chan, V. B. 1967. A study of some factors influencing the orientation beha-viour of the ambrosia beetle Trypodendron lineatum (Olivier) (Coleoptera Scolytidae). M.Sc. Thesis, University of British Columbia •Chapman, J.A. 1955. Physiological and biological studies of the ambrosia beetle, Trypodendron lineatum (Oliv.) and the Douglas-fir beetle, Dendroctonus pseudotsugae (Hopk.). Interim Rept. 195b-2, Can. Dept. Agr. Science Ser., For, Biol. Div. •Chapman, J.A. 1956. Studies on the physiology of the Ambrosia Beetle Trypodendron in relation to its ecology. Proc. X Int. Congr. Ent. hi 375-380 •Chapman, J.A. 1962. Field studies on attack flight and log selection by the ambrosia beetle Trypodendron lineatum (Oliv.) (Coleoptera: Scolytidae). Can. Ent. 9h'- 7li-92 •Chapman, J.A. 1966. The effect of attack by the ambrosia beetle Trypodendron  lineatum (Olivier) on log attractiveness. Can. Ent. 98: 50-^ 9* •Chapman, J.A., S.H. Farris, and J.M. Kinghorn. 1963. Douglas-fir sapwood starch in relation to log attack by the ambrosia beetle, Trypodendron. For. Sci. 9: l30-li39, 86 *Chapman, J.A., and J.M. Kinghorn. 1958. Studies of flight and attack acti-vity of the ambrosia beetle, Trypodendron lineatum (Oliv.), and other scolytids. Can. Ent. 90: 362-372 C^hapman, K.M. 1965. Campaniform sensilla on the tactile spines of the legs of the cockroach. J. Exp. Biol. Ij2: 191-203 *Dethier, V.G. 1952. Adaptation to chemical stimulation of the tarsal receo-tors of the blowfly. Biol. Bull. 103(2): 178-189 •K-Dethier, V.G. 195b. The physiology of olfaction in insects. Ann. N.Y. Acad. Sci. £8: 139-157 *Dethier, V.G. 1955. The physiology and histology of the contact chemo-receptors of the blowfly. Quart. Rev. Biol. 30 (-h): 3b8-371 *Dethier, V.G. 1962. Chemoreceptor mechanisms in insects. Soc. Exp. Biol. Symp. 16: 180-196 Dethier, V. G. 1963. The Physiology of Insect Senses. J. Wiley, N. Y. 266 p. Dethier, V.G.,. Larsen, J.R., and J.R. Adams. 1963. The fine structure of the olfactory receptors of the blowfly. In: First Int. Symp. on Olfac-tion and Taste, Stockholm 1962. (Zotterman, Y., Ed.). Pergamon press, Oxford, or N.Y., MacMillan. 105-110 Dethier, V. G., and M.L. Wolbarsht. 1956. The electron microscopy of chemo-sensory hairs. Experientia 12: 335-337 #Dyer, E.D.A. 1962. The effect of exposure of hibernation sites on the time of Trypodendron spring flight. Can. Ent. 9b(9): 910-915 *Dyer, E.D.A. 1963. Distribution of Trypodendron attacks around the-circum-ference of logs. Bi-mo. Prog. Rep. Can. Dept. For. 19(2): 3-h . #Dyer, E.D.A., and J.M. Kinghorn. 1961. Factors influencing the distribution of overwintering ambrosia beetles, Trypodendron lineatum (Oliv.). Can. Ent. 93: 7b6-759 *Evans, D.R. 1961. The effect of odours on ingestion by the blowfly. J. Ins. Physiol. 7: 299-30b #Evans, D.R. 1963. Chemical structure and stimulation by carbohydrates. In: Olfaction and Taste, Y. Zotterman, ed. MacMillan Co., N.Y., 185-176 #Evans, D.R., and D. Mellon, Jr. 1962. Stimulation of a primary taste recep-tor by salts. J. Gen. Physiol. L(5(b): 651-661 *Feir, D., J.I. Lengy, and W.B. Owen. 1961. Contact chemoreception in the mosquito, Culiseta inornata (Williston); sensitivity of the tarsi and labella to sucrose and glucose. J. Ins. Physiol. 6: 13-20 *Francia, F.C. 1965. Studies of some aspects of behaviour in the ambrosia beetle Trypodendron lineatum Oliv. Ph D Thesis, University of British Columbia 87 *George, M, 1963. Studies on Campodea (fiplura): the anatomy of the glands and sense-organs of the head. Quart. J. Micr. Sci. l O L : 1-21 *Gillary, H.L. 1966. Stimulation of the salt receptor of the blowfly: I. NaCl II. Temperature III. the alkali halides. J. Gen. Physiol. 50: 337-368 #G6rner, P. 1965. A proposed transducing mechanism for a multioly-innervated mechanoreceptor (trichobothrium) in spiders. Cold Spring Harbor Symp. Quant. Biol. 30: 69-73 *Graham, K. 1959. Release by flight exercise of a chemotropic response from photopositive domination in a Scolytid beetle. Nature 18L: 283-28L *Graham, K. 1961. Air-swallowing: a mechanism in photic reversal of the beetle Trypodendron. Nature 191: 519-520 Graham, K., and A.E. Werner. 1956. Chemical aspects of log selection by ambrosia beetles. Can. Dept. Agr. For. Biol. Div. Interim Rept. 1955-1 Victoria, (unpubl.) Gray, E. G. I960. The fine structure of the insect ear. Phil. Trans. B 2b3: 75-91 •w-Hardee, D. D., E.B. Mitchell, and P.M. Huddleston. 1966. Chemoreception of attractants from the cotton plant by Boll weevils, Anthonomus grandis (Coleoptera: Curculionidae). Ann. Ent. Soc. Amer. 59(5)' 867-068 *Hardee, D.D., E.B. Mitchell, and P.M. Huddleston. 1966. Effect of age, nutrition, sex, and time of day on response of boll weevils to an attrac-tant from cotton. Ann. Ent. Soc. Amer. 59(5): 1021-1025 *Hodgson, E.S. 196b. Chemoreception. In: Physiology of Insecta, Vol. I. M. Rockstein, ed. Academic Press, p. 363-396 Hodgson, E.S. 1965. The chemical senses and changing viewpoints in sensory physiology. Viewpoints in Biology. Ed. J.D. Carthy and C. L. Duddington p.'83-12b Kay, D.H. 1965. Techniques for Electron Microscopy.2nd Ed. Blackwell Scient. Publ..Oxford Kushida, H. 1966. Block staining with lead acetate. J . Electron Microscopy 15(2): 90-92 Kuwabara, M. 1963, Tarsal chemoreception in the butterfly, Vanessa indica. Proc. XVI Int. Congr. Zool. 3: 96-97 #Lacher, V. 196b. Elektrophysiologische Untersuchungen an einzelnen Rezep-toren ftir Geruch, Kohlendioxyd, Luftfeuchtigkeit und Temperatur auf den Antennen der Arbeitsbiehne und der Drohne (Apis mellifica L.). Z. Vergl. Physiol. L8: 587-623 *Lacher, V., and D. Schneider. 1963. Elektrophysiologischer Nachweis der Riechfunktion der Porenalatten (Sensilla Placodea) auf den Antennen <-'er Drohne und der Arbeitsbiene (Apis mellifera L.). Z. Vergl. Physiol. b7: 27b-278 88 Larsen, J.R. 1962. The fine structure of the labellar chemosensory hairs of the blowfly, Phormia regina Meig. J . Ins. Physiol. 8: 683-691 Larsen, J.R. 1963. Fine structure.of the interpseudotracheal papillae of the blow fly. Science 139: 3hl Larsen, J.R., and V* G. Dethier. 1963. The fine structure of the labellar and antennal chemoreceptors of the blowfly Phormia regina. Proc. XVI Int. Congr. Zool. 3.' 81-83 Luft, J.H. 1961. Improvements in epoxy resin embedding methods. J. Cell Biol. 9: ii09-ljlii Mclndoo, N.E. 19-lb. The olfactory sense of insects. Smiths. Inst. Publ. Misc. Coll. 63: 1-63 Mclndoo, N.E. 1926. Senses of the cotton boll weevil. An attempt to explain how plants attract insects by smell. J. Agr. Res. 33: IO95 -III4I Molenaar, L. J., and B. Schotanus. 1962. An improved method for making carbon films for electron microscooy. Science and Industry N. V. Philips 9(1): 214-25 •K-Morita, H. 1963. Generator potential of insect chemoreceptors. Proc. XVI Int. Congr. Zool. 3} 105-106 *Nicklaus, R. 1965. Me Erregung einzelner Fadenhaare von Periplaneta americana in AbhMngigkeit von der Grttsse und Richtung der Auslenkung. Z. Vergl. Physiol. 50: 331-362 Noble-Nesbitt, J. 1963a. The fully formed intermoult cuticle and associated structures of Podura aquatica (Collembola). Quart. J. Micr. Sci. IOI4: 253-270 Noble-Nesbitt, J. 1963b. The cuticle and associated structures of Podura  aquatica at the moult. Quart. J. Micr. Sci. lT^: 369-391 Osborne, M.P. 1963. The sensory neurones and sensilla in the abdomen and thorax of the blowfly larva. Quart. J. Micr. Sci. 10ib: 227-2L1 Osborne, M.P. 196b. Sensory nerve terminations in the epidermis of the blow-fly larva. Nature 201: 526 Osborne, M.P., and L.H. Finlayson. 1965. An electron microscope study of the stretch receptor of Antheraea pernyi (Lepidoptera, Saturniidae). J. Ins. Physiol. 11: 703-710 *0wen, W.B. 1963. The contact chemoreceptor organs of the mosquito and their function in feeding behaviour. J. Ins. Physiol. 9: 73-88 Peters, W. I960. Morphologische Untersuchungen an Chemischen Sinnesorganen der Schmeissfliege Calllphora erythrocephala Mg. (Diptera). XI Int. Congr. Ent. Wien, :1J07-II09 : *Peters, W,, and S. Richter. 1963. Morphological Investigations on the sense organs of the labella of the blowfly, Calliphora erythrocephala Mg. Proc. XVI Int. Congr. Zool. 3: 89-92 89 Prestage, J.J,, E. H. Slifer, and L. B. Stephens. 1963. Thin-walled sensory-pegs on the antenna of the termite worker, Reticulitermes flavipes. Ann. Ent. Soc. Amer. 56: 87I4-878 Pringle, J.W. S. 1938a. Proprioception in insects. I. A new type of mechani-cal receptor from the palps of the cockroach. J. Exp. Biol. 13>: 101-113 Pringle, J.W. S. 1938b. Proprioception in insects. II. The action of the campaniform sensilla on the legs. J. Exp. Biol, 15: Hli-131 •Prosser, CL,, and F. A. Brown. 1961. Comparative Animal Physiology. W.B. Saunders Co. Richardson, K.C., L.J. Jarett, and E.H. Finke, I960. Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain. Techn. 35: 313-323 •Riegert, P.Wm. I960. The humidity reactions of Melanoplus bivittatus (Say) (Orthoptera, Acrididae): antennal sensilla and hygro-reception. Can. Ent. 92(8): 561-570 •Roth, L.M. 195l. Loci of sensory end-organs used by mosquitoes (Aedes aegypti, L. and Anopheles quadrimaculatus Say) in receiving host stimuli. Ann. Ent. Soc. Amer. W±(l): 59-71* •Roth, L.M., and E.R. Willis. 1951. Hygroreceptors in coleoptera. J. Exp. Zool. 117: 1J51-1J88 •Roth, L.M., and E.R. Willis. 1952. Possible hygroreceptors in Aedes aegypti (L.) and Blattella germanica (L.). J. Morph. 9 l ( l ) : 1-llj •Rudinsky, J.A., and G.E. Daterman. 1961a. Field studies on flight patterns and olfactory responses of ambrosia beetles in Douglas-fir forests of Western Oregon. Can. Ent. 96(10): 1339-1352 •Rudinsky, J.A., and G.E. Daterman. 196bb. Responses of the ambrosia beetle Trypodendron lineatum (Oliv. ) to a female-produced pheromone. Zeitschr. f. Angew. Ent. 5Jj(3): 300-303 Sabatini, D. D., K. Bensch, and R. J. Barrett. 1963. Cytochemistry and electron microscopy. The preservation of cellular ultrastructure and enzymatic activity by aldehyde fixation. J. Cell Biol. 17: 19-58 •Schmidt, G. I960. Sinnesorgane bei Ameisenlarven. (Form. Hym. Ins.). XI Int. Congr. Ent. Wien : L03-1J07 •Schneider, D. 1957. Elektrophysiologische Untersuchungen von Chemo- und Mechanorezeptoren der Antenne des Seidenspinners Bombyx mori L. Z. Vergl. Physiol. LO: B-hl •Schneider, D. 1962. Electrophysiological investigation on the olfactory specificity of sexual attracting substances in different species of moths. J. Ins. Physiol. 8: 15-30 •Schneider, D. 1963. Function of insect olfactory sensilla. Proc. XVI Int. Congr. Zool. 3: 8b-85 90 Schneider, D. 1961. Insect Antennae. Ann. Rev. Ent. £: 103-122 •Schneider, D., and J. Boeckh. 1962. Rezeptor Potentiale und Nervenimpulse einzelner olfaktorischer Sensillen der Insektenantenne. Z. Vergl. Physiol. h$t ]J05-IJ12 Schneider, D., V. Lacher, and K,Kaissling. 196L. Die Reaktionsweise und das Reaktionspektrum von Riechzellen bei Antheraea oernyi (LepidoDtera, Saturniidae). Z. Vergl. Physiol. b_8: 632-662 Schwartzkopff, J. 196Ij. Mechanoreception. In: Physiology of Insecta, Vol. I. M. Rockstein, ed. Academic Press, p. 509-561 Slifer, E.H. 1961. The fine structure 6f insect sense organs. Int. Rev. Cyt. 11: 125-159 •Slifer, E.H. 1963. Pine structure of insect olfactory receptors. Proc. XVI Int. Congr. Zool. 3: 79-80 Slifer, E.H., J.J. Prestage, and H.W. Beams. 1957. The fine structure of the long basiconic sensory pegs of the grasshopper (Orthoptera, Acridi-dae) with special reference to those on the antennae. J. Morph. 101: 359-397 Slifer, E.H., J.J. Prestage, and H.W. Beams. 1959. The chemoreceptors and other sense organs on the.antennal flagellum of the grasshopper (Orthoptera, Acrididae). J. Morph. 105: 11*5-192 Slifer, E-H., and S.S. Sekhon. 1961. Fine structure of the sense organs on the antennal flagellum of the honey bee, Apis mellifera Linnaeus. J. Morph. 109: 351-381 Slifer, E.H., and S.S. Sekhon. 1962. The fine structure of the sense organs on the antennal flagellum of the yellow fever mosquito, Aedes aegypti (Linnaeus). J.Morph. I l l : 1)9-67 Slifer, E.H.., and S.S. Sekhon. 1963. Sense organs on the antennal flagellum of the small milkweed bug, Lygaeus kalmii Stal (Hemiptera, Lygaeidae). J. Morph. 112: 165-193 Slifer, E.H., and S.S. Sekhon, 196ha. Fine structure of the thinwalled senso-ry pegs on the antennae of a beetle, Popilius disjunctus (Coleoptera: Passalidae). Ann. Ent. Soc. Amer. 57: 51jl-5bfl . Slifer, E.H., and S.S. Sekhon. 196hb. Fine structure of the sense organs on the antennal flagellum of the flesh fly, Sarcophaga argyrostoma R.-D. (Diptera, Sarcophagidae). J. Morph. l l l i ; 185-208 Slifer, E.H., and S.S. Sekhon. 196bc The dendrites of the thin-walled olfactory pegs of the grasshopper (Orthoptera, Acrididae). J. Morph. l l l i : 393-blO Slifer, E.H., S.S. Sekhon, and A.D. Lees. 196)4. The sense organs on the antennal flagellum of aphids (Homoptera) with special reference to the plate organs. Quart. J. Micr. Sci. 105: 21-29 9 1 Snodgrass, R.E. 1926. The morphology of insect sense organs and the sensory nervous system. Smiths. Misc. C o l l . 77,: 1-80, 32 f i g s . Snodgrass, R.E. 1935. Principles of Insect Morphology. McGraw-Hill Book Co. *Steinhardt, R.A., H. Morita, and E.S. Hodgson. 1966. Mode of action of straight chain hydrocarbons on primary chemoreceptors of the blowfly, Phormia regina. «T. C e l l . Physiol. 67(1): 53-62 Stttrckow, B. 1963. Electrophysiological studies of a single taste hair of the f l y during stimulation by a flowing system. Proc. XVI Int. Congr. ' Zool. 3: 102-10b *Stilrckow, B, 196b. Some common features of three types of insect s e n s i l l a . Experientia 20: 509-511 Thurm, U. 1963. Die Beziehungen zwischen mechanischen reizgrossen und s t a t i o -naVen ErregungszustSnden bei Borstenfeld-Sensillen von Bienen. Z. Vergl. Physiol. b6: 351-382 Thurm, U. 196ba. Mechanoreceptors i n the c u t i c l e of the honey bee: f i n e structure and stimulus mechanism. Science lb5: 1063-1065 Thurm, U. 196bb. Das Rezeptorpotential einzelner mechanorezeptorischer Zellen von Bienen. Z. Vergl. Physiol. b_8: 131-156. Thurm, U. 1965. An insect mechanoreceptor. Part I. Fine structure and adequate stimulus. Cold Spring Harbor Symp. Quant. B i o l . 30: 75-82 Part I I . Receptor potentials. Ibid. p. 83-9b Uga, S., and Kuwabara, M. 1965. On the fine structure of the chordotonal sensillum i n antenna of Drosophila melanogaster. J. Electron Micros, lb (3): 173-181 Wigglesworth, V.B. 1959. The histology of the nervous system of an insect Rhodnius prolixus (Hemiotera). I. The peripheral nervous system. Quart. J. Micr. Sci. 100: 285-298 •Wolbarsht, M.L. 1965. Receptor s i t e s i n insect chemoreceptors. Cold Spring Harbor Symp. Quant. B i o l . 30: 281-288 •Zacharuk, R. Y. 1962a. Some histochemical characteristics of tissues i n larvae of Ctenicera destructor (Brown) (Coleoptera, Elateridae), with special reference to cutaneous s e n s i l l a . Can. J. Zool. b_0: 733-7b6 *Zacharuk, R. Y. 1962b. Sense organs of the head of larvae of some Elateridae (ColeoDtera): t h e i r d i s t r i b u t i o n , structure, and innervation. J. Morph. 111(1): 1-31 *Zacharuk, R.Y. 1962c. Exuvial sheaths of sensory neurones i n the larva of Ctenicera destructor (Brown) (Coleoptera, Elateridae). J. Morph. I l l : 35-b7 

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}]}"
                            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:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0104522/manifest

Comment

Related Items