Sensilia on the sexually dimorphic antennae of the blister beetle, Meloe campanicollis, were primarily sensilla chaetica with scattered socketed and non-socketed sensilla basiconica. Forked chaetifonn sensilla on the female\u27s first segment are displaced by the antennal socket rim when the male grasps and lifts her antennae with segments 5 to 7 of his antennae. Segments 5 to 7 lack dense sensilla chaetica and have only patches of shorter sensilla. The segments also contain a high density of epidennal gland ducts compared to other segments. Maxillary palpi apices were similar in males and females, but the female\u27s labial palpi contained fewer narrow and many more short, broad sensilla basiconica than the male·s

Bland, R. G

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R. G Bland

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 (Coleoptera: Meloidae)

Valparaiso University

The Great Lakes Entomologist Volume 19 Number 4 - Winter 1986 Number 4 - Winter 1986 Article 4 December 1986 Antennal and Mouthpart Sensilla of the Blister Beetle. Meloe Campanicollis (Coleoptera: Meloidae) R. G. Bland Central Michigan University Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Bland, R. G. 1986. "Antennal and Mouthpart Sensilla of the Blister Beetle. Meloe Campanicollis (Coleoptera: Meloidae)," The Great Lakes Entomologist, vol 19 (4) Available at: https://scholar.valpo.edu/tgle/vol19/iss4/4 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1986 THE GREAT LAKES ENTOMOLOGIST 209 A~TE:,\~AL A.,\1) MOUTHPART SENSILLA OF THE BLISTER BEETLE, .lfELOE C4MPANICOLLIS (COLEOPTERA: MELOIDAE) R. G. Bland l ABSTRACT Sensilia on the sexually dimorphic antennae of the blister beetle, Meloe campanicollis, were primarily sensilla chaetica with scattered socketed and non-socketed sensilla basiconica. Forked chaetifonn sensilla on the female's first segment are displaced by the antennal socket rim when the male grasps and lifts her antennae with segments 5 to 7 of his antennae. Segments 5 to 7 lack dense sensilla chaetica and have only patches of shorter sensilla. The segments also contain a high density of epidennal gland ducts compared to other segments. ~Iaxillary palpi apices were similar in males and females, but the female· s labial palpi contained fewer narrow and many more short, broad sensilla basi­conica than the male·s. North .-\merican blister beetles (Meloidae) in the genus Meloe are dull black beetles, often with metallic blue. green, or purple hues. These soft-bodied beetles lack hind wings or ha\e abbre\iated. basally imbricated elytra. The subgenus Meloe is characterized, in part. by a modification of the male's antennae that functions to receive the female's antennae during courtship. Pinto and Selander (1970) described the sexual behavior of Meloe species in their re\iew of the bionomics and classification of New World Meloe. The male's antennation of the female is the dominant display activity. The male mounts the female dorsally and periodically attempts to grasp the basal or middle region of the female's antennae with segments .5 to 7 of his corresponding antennae. The three segments form a clasp that secures the antenna from underneath by bending at the articulation f segments 6 and 7. He then raises his head slightly which pulls the female's antennae upward. Antennal stroking wward the distal end is the most common motion and appears to be the result of unsu.;:cessful attempts to grasp the female's antennae, such as when they are not easily accessible or are mo\·ing. rather than a consummatory act. Palpation of the female is a second display motion that occurs during antennation, whereby the male uses his ma"(iliaI! palpi to rub the top and front f her head. The specialized u...-.e of the clasping region of the male's antennae indicated that specific sense r.:ceptors might be present in that region, and complementary mechanoreceptors that fe5p..."Od w stroking may occur on the female's antennae. Therefore the morphology and distribution of all sensilla on the antennae and apex of the maxillary and labial palpi of -'1e/ot' campanicollis Pinto and Selander were characterized with a scanning electron mlcros.:-ope. :Bi0I~~ Deparunent. Central ~lichigan Cniyersity. ~lt. Pleasant. MI 48859 1Bland: Antennal and Mouthpart Sensilla of the Blister Beetle. <i>Meloe CPublished by ValpoScholar, 1986210 THE GREAT LAKES ENTOMOLOGIST VoL 19, No.4 METHODS AND MATERIALS Specimens were collected in central Michigan in October 1984. Antennae and mouthparts were sonicated in a surfactant and air dried. They were sputter-coated with 30 nm of gold and observed with an AMR- 1200 scanning electron microscope. RESULTS Antennae The antennae of males and females are II-segmented and dimorphic (Fig. 1). Sensilla have been placed into five groups, A to E, and all sensillar types are found on the antennae of males and females except for two kinds of sensilla basiconica with sockets that were not observed on the female's antennae. A. Sensilla chaetica (Fig. 2). These ridged receptors represent over 90% of the antennal sensilIa. Long sensilla, 80-240 [.Lm in length, are on segments I to 5 and 7 of the male's antenna and I to 7 on the female's. The longest sensilla occur on segments I and 2. Medium-length sensilla, 35-65 [.Lm long, occur on segments 6 and 8 to 11 of the male's antennae and 4 to lIon the female's. B. Forked chaetiform sensilla (Figs. 3,4). Approximately 32 bifurcated chactiform sensilla occur on the dorsal, lateral, and lateroventral portions of the basal region of segment one. They range from 20 to 11  J.1m in length. Some receptors are trifurcated on the female. When the antennae are raised, the forked sensilla shown in Figure 4 contact the rim of the antennal socket and are pressed forward. C. Sensilla basiconica with sockets. Non-ridged, short sensilla, often with a bulbous socket (Fig. 5) are scattered on all segments and range from 10 to 14 [.Lm in length. They also occur in two to three irregular rows near the tip of segment 10 on the male's antennae. Scattered, stout sensilla 9-15 [.Lm long and with a smooth surface are found on segment 1. A few stout, ridged, uniporous sensilla (Fig. 6) averaging 30 [.Lm in length arc scattered on the dorsal surface of segment 5 on the male, About 10 ridged, slender receptors (Fig. 9), 25 J.1m long, occur in the inner and outer patches of sensilla on segment 6 of the male, D. Sensilla basiconica without sockets. Non-ridged, short receptors occur on segments 10 and 11, with most on segment 11. The base enlarges into a bulbous projection that is continuous with the cuticle. They are uniporous and average 12 [.Lm in length. E. Domed sensilla basiconica (Fig, 7). Approximately 40 short, domed sensilla are scattered primarily over the basal two-thirds of egment 9 on the male's antennae. They are in sockets and are 6-10 [.Lm in diameter and 5 J.1m high. These sen sill a are also scattered in small numbers on segments 1 to 3 and 11 of the female's antennae. Segments 5 to 7 of the Male's Antenna In addition to having a different shape and arrangement from the other segments, these three segments also differ in two more ways. 1. They have fewer and shorter sensilla on the surfaces that contact the female's antenna (Fig. 8). On segment 6, a patch of 25-32 sensilla occur on the inner and outer halves of the dorsal surface. Most are medium length (35-50 [.Lm), ridged sensilla chaetica as described in group A. About 10 short, ridged basiconic sensilla (Fig. 9) (group C) form the remainder on this segment; some also occur on the lower anterior face of segment 5. The lower posterior face of segment 7 has a small inner patch of sensilla similar to the inner patch of segment 6. 2The Great Lakes Entomologist, Vol. 19, No. 4 [1986], Art. 4https://scholar.valpo.edu/tgle/vol19/iss4/41986 THE GREAT LAKES ENTOMOLOGIST 211 Figs. 1-4. (I) Antennae of a male (Al and female (B) M. campanicollis. Segments 5-7 are used to grasp the female's antenna or they may stroke her antenna if grasping is unsuccessful (lOX). (2) Sensilla chaetica, medium length, on the dorsal surface of segment 5. These and the long sensilla chaetica are the most co mon receptors. This segment has a high density of epidermal gland ducts (675XL (3) Forked chaetiform sensilla on segment 1 (675X). (4) Arc of forked and single-tipped chaetiform sensilla at the base of segment 1. The longer receptors are displaced forward by the rim of the antennal socket when the antenna is raised (17 5X). 2. The density of epidermal gland ducts (Figs. 2,9) on the contacting surface of the three segments increases up to twice that of the non-contacting surface and nearly five times that of the remaining segments (Table 1). The ducts range from 0.6 to 1.5 !Lm in diameter. Mouthparts The terminal segment of the maxillary palpus is a flattened cylinder with a shallow furrow at its apex (Fig. 10). The furrow on the male's palpus averages 40 !Lm in width and 400 !Lm in length, and it contains about 110 basiconic sen sill a (Fig. 11). Approximately 70 sensilla are broad and 7-43 !Lm long; 40 are narrower and 5-8 !Lm long. Tenninal pores were observed on both narrow and broad sensilla. The furrow on the female's palpus is (60 x 700 !Lm) and has approximately \07 broad and 88 narrow sensilla to total 195 receptors. 'Ine apex of the male' s labial palpus has a furrow that averages 30 !Lm wide and 350 !Lm long. Approximately 70 basiconic sensilla are present and consist of about 20 broad sensilla 5-10 !Lm long. and 45 narrower sensilla 4-5 !Lm long. Terminal pores were 3Bland: Antennal and Mouthpart Sensilla of the Blister Beetle. <i>Meloe CPublished by ValpoScholar, 1986212 THE GREAT LAKES ENTOMOLOGIST VoL 19, No.4 Figs. 5-9. (5) Sensillum basiconicum with a bulbous socket on segment 10 (3970X). (6) Sensillum basiconicum with ridges and a terminal pore on segment 5 of the male (1590X). (7) Domed sensillum basiconicum (3970X). (8) Segments 5,6, and 7 of the male's antenna illustrating the paucity of sensilla on the surfaces that grasp the female's antenna (30X). (9) High density of spidermal gland ducts on segment 6 of the male's antenna; also shown is a ridged and slender sensillum basiconicum (lIIOX). observed only on the narrower sensilla. There were a few very short, broad sensilla 2-4 !Lm long. The female's labial furrow was 40 !Lm wide and 350 !Lm long. About 16 sensilla were broad, 19 were narrower, and 48 were very short and broad. DISCUSSION Scanning electron microscope studies of antennal sensilla and, to a lesser extent, mouthpart sensilla of adult beetles have been conducted by Mustaparta (1973), Payne et al. (1973), Dyer and Seabrook (1975), Hatfield et aL (1976), Staetz et al. (1976), Smith et al. (1976), Harbach and Larson (1977), Juberthie and Massoud (1977), Peck (1977), Dickens and Payne (1978), Bland (1981), Whitehead (1981), and Hallberg (1982a,b). Investigations that have emphasized cell ultrastructure by utilizing transmission electron microscopy were reviewed by Zacharuk (1985). 4The Great Lakes Entomologist, Vol. 19, No. 4 [1986], Art. 4https://scholar.valpo.edu/tgle/vol19/iss4/41986 THE GREAT LAKES ENTOMOLOGIST 213 Table I. Mean number of epidermal gland ducts per mm2 on antennal segments of male and female beetles. Ducts/mm2 Segment Male Female 2 3 4 5 6 7 8 9 10 II 1-4 + 8-11 5-7 1-12 IA L7 L7 2.1 10.53 19.5h 14.0" 3.5 3.5 4.0 6.0 Average 0.7 1.8 2.0 2.0 0.7 0.5 0,8 IA L7 2.5 2.5 3.0 L8 14,7 0.7 6.2 L5 a14,2/mm2 on anteIior (contacting) side; 7.5/mm2 on dorsal and ventral sides. bl1.21mm2 on ventral side. c 19 A'mm2 on posteIior (contacting) side; 9.lImm2 on dorsal, ventral and anterior sides. figs. 10.. 11. 'II::"\: 11, ~arrow (AI and broad IBI basiconic sensilla on the apex of a maxillary palpus: I p I ten:nina1 pore ,3485X,. The sensilla on the antennae of .U. campanicollis are very similar in external morphology to many of those of other beetles although the seosilla combinations vary for each spn:ies. There were DO uDUSual mechanoreceptors on the female's antennae that might indicate a differential response to antennation by the male. The predominant sensilla chaetica are typical of mechanoreceptors. although there are also chemoreceptors with pointed tips as well as some with an additional mechanoreceptive function (McIver 1975 L The tactile function f these sensilla is supported by the observation that the 5Bland: Antennal and Mouthpart Sensilla of the Blister Beetle. <i>Meloe CPublished by ValpoScholar, 1986214 THE GREAT LAKES ENTOMOLOGIST Vol. 19, No.4 antennation of the female by the male has a calming effect on the female and elicits the first sign offemale receptiveness (Pinto and Selander 1970). When the female's antennae are raised by the male, the arc of forked mechanoreceptors on the basal portion of segment one is displaced by the socket rim. Their displacement may increase her receptivity to genital probing by the male as observed by Pinto and Selander (1970). The sensilla basiconica with sockets are most likely chemoreceptors. Sensilla basiconica with expanded bases and without sockets may be hygro- or thermoreceptors, based on similar non-porous sensilla identified by Altner et al. (1983). As with M. campanicollis, they found small numbers of these sensilla concentrated near the tip and distributed in low numbers on the rest of the antenna of a variety of insects. The domed bas iconic sensilla lack a terminal pore and resemble mechanoreceptive campaniform sensilla, except that they rise from a relatively deep socket. AItner et al. (1983) described a similarly shaped hygro- or thermoreceptor on a carabid beetle although it also had a shallower socket. The lack of long sensilla chaetica and fewer medium-length sensilla chaetica on the clasping segments of the male's antenna may provide a more solid and stable surface as well as more surface for grasping the female's antenna. The patches of shorter sensilla then are available to supply a more direct mechanoreceptive function since they are not overlaid by the larger sensilla. The reason for the high density of epidermal gland ducts on the three segments is not readily apparent. They are responsible for secreting the cement layer of the epicuticle (Wigglesworth 1972). If these ducts release the same amount f fluid as on other segments, their high density may result in an overflowing effect to produce a thick and smooth buildup of the cement layer. Observations directly into the ducts showed no evidence of a sensillum. However, some cuticular pits are known to have deeply recessed sensilla ampullacea or campaniforma (Zacharuk 1985). An ultrastructural study i  necessary to elucidate the nature of these ducts and determine the function of the various sensilla on the antennae and mouthparts. The apex of the maxillary and labial palpi had no unusual sensilla present. The male's maxillary palpus had 50% more sensilla per unit area than the female's, and 9% more broad sensilla and 9% fewer narrow sensilla. The greater density on the male may increase his stimulus receptivity during his palpation of the female. Although the sensilla on the apex ofthe male's labial palpus were only 14% more dense than those on the female's, there was a notable diff rence in the percentages of sensillar types. On the male's apex, 64% were the narrower type compared to 23% on the female, and only 7% were short and broad compared to 58% on the female. Pinto and Selander (1970) briefly described the feeding and grooming habits of Meloe spp. and did not identify any differences between males and females. Thus the number of short, broad sensilla on the female may indicate their use in the selection, excavation, and filling of ovipositional sites as described by Pinto and Selander (1970). LITERATURE CITED Altner, H., L. SchaBer-Seizer, H. Stetter, and I. Wohlrab. 1983. Poreless sensilla with inflexible sockets. A comparative study of a fundamental type of insect sensilla probably comprising thermo- and hygroreceptors. Cell Tissue Res. 234:279-307. Bland, R. G. 1981. Antennal sensiIla of the adult alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae). Int. J. Insect Morpho!. Embryo!. 10:265-74. Dickens, 1. C, and T. L. Pay e. 1978. Structure and function of the sensilla on the antennal club of the southern pine beetle, Dendroctonus frontalis (Zimmerman) (Coleoptera: Scolytidae). Int. 1. Insect Morpho!. Embryo\. 7:251-65. Dyer, L. 1., and W. D. Seabrook. 1975. SensiIla on the antennal flagellum of the sawyer beetles Monochamus notatus (Drury) and Monochamus scutellatus (Say) (Coleoptera: Cerambycidae).1. Morpho!. 146:513-531. HaBberg, E. 1982a. Sensory organs in Ips typographus (Insecta: Coleoptera)--fine structure of antennal sensiIla. Protoplasma 111:206-14. 6The Great Lakes Entomologist, Vol. 19, No. 4 [1986], Art. 4https://scholar.valpo.edu/tgle/vol19/iss4/41986 THE GREAT LAKES ENTOMOLOGIST 215 Hallberg, E. 1982b. Sensory organs in Ips rypographus (Insecta: Coleoptera)-fine structure of the sensilla of the maxillary and 1 abial palps. Acta Zoo!. 63: 191-98. Harbach, R. E., and J. R. Larson. 1977. Fine structure of antennal sensilla of the adult mealworm beetle. T nebrio molitor L. (Coloptera: Tenebrionidae). Int. 1. Insect Morpho!. Embryo\. 6:41-60. Hatfield. L. D .. J. L. Frazier. and L. B. Coons. 1976. Antennal sensilla of the pecan weevil Curculio caryae (Hom) (Coleoptera: Curculionidae). Int. J. Insect Morpho\, Embryol. 5:279-87. Juberthie, C. and Z. ~fassoud. 1977  L 'equipement sensoriel de I'antenne d'un Coleoptere troglobie. Aphaenops cryticola Linder (Coleoptera: Trechinae). Int. J. Insect MorphoL Embryol. 6:147-60. McIver. S. B. 1975. Structure of cuticular mechanoreceptors of arthropods. Ann. Rev. EntomoL 20:381-97. Mustaparta. H. 1973. Olfactory sensilla on the antennae of the pine weevil, Hylobiusabietis. Z. Zellforsch. Mikrosk. AnaL 144:559-71. Payne. T. L.. H. A ~toeck, C. D. Willson, R. N Coulson, and W. J. Humphreys. 1973. Bark beetle olfaction-II. Antennal morphology of sixteen species of Scolytidae (Coleoptera). Int. J. Insect Morpho!. EmbryoL 2:177-92. Peck. S. B. 1977. All unusual sense receptor in internal antennal vesicles of Ptomaphagus (Coleoptera: Leiodidae). Canadian Entomol. 109:81-86. Pinto. J. D .. and R. B. Selander. 1970. The bionomics of blister beetles of the genus Meloe and a classification of the New World species. Illinois BioI. Monog. 42. 222 pp. Smith. C. ~t . J. L. Frazier, L. B. Coons, and W. E. Knight. 1976. Antennal sensillaof the clover head weevil H)pera meles (F.) (Coleoptera: Curculionidae). Int. 1. Insect ~lorphol. Embryol. 6:349-55. Staetz. C. A .. H. J. Ball. and S. D. Carlson. 1976. Antennal morphology of Diabrotica drgifera adults (Coleoptera: Chrysomelidae). Annals Entomol. Soc. Amer. 69: 695-98. Whitehead. A. T. 1981. Ultrastructure of sensilla of the female mountain pine beetle, Dendrocronus ponderosae Hopkins (Coleoptera: Scolytidae). Int. 1. Insect Morphol. Embrvol. 10: 19-28. \\"iggles'v;orth. V. B. 1972. The principles of insect physiology. Methuen, London. Zacharuk. R. Y 1985. Antennae and sensilla. pp. 1-69 in G. A. Kerkut and L. L Gilbert (cds. t. Comprehensive insect physiology, biochemistry and pharmacology Vo!. 6. Pergamon Press. N.Y. 7Bland: Antennal and Mouthpart Sensilla of the Blister Beetle. <i>Meloe CPublished by ValpoScholar, 1986

Antennal and Mouthpart Sensilla of the Blister Beetle. \u3ci\u3eMeloe Campanicollis\u3c/i\u3e (Coleoptera: Meloidae)

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Antennal and Mouthpart Sensilla of the Blister Beetle. \u3ci\u3eMeloe Campanicollis\u3c/i\u3e (Coleoptera: Meloidae)

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