Elateriformia (Coleoptera)

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J. F. Lawrence, A. M. Hastings, M. J. Dallwitz, T. A. Paine and E. J. Zurcher

DRILIDAE (anelytrous females)

Classification. Polyphaga: Elateriformia.

Distribution. Species of Drilus are known from Europe, Africa, Asia Minor, Central Asia and Sri Lanka, Malacogaster occurs in southern Europe, northern Africa, Asia Minor and the Canary Islands, Selasia is restricted to Africa, and Pseudeuanoma occurs in eastern Europe and Asia Minor.

Biogeographic regions: Palearctic, Afrotropical, Oriental.

Biology. Larvae of Drilus and Selasia are known to feed on snails; females lack elytra and are more or less larviform.

References

Audouin, V. 1824. Lettre sur la génération des insectes. Annales des Sciences Naturelles 2: 281–285, pl. 7.

Barker, J. F. 1969. Notes on the life cycle and behaviour of the drilid beetle Selasia unicolor (Guérin). Proceedings of the Royal Entomological Society of London (A) 44: 169–172, 1 pl.

Crowson, R. A. 1972. A review of the classification of Cantharoidea (Coleoptera), with the definition of two new families, Cneoglossidae and Omethidae. Revista de la Universidad de Madrid, 21 (82): 35–77.

Latreille, P. 1824. Note sur mémoire de M. le Comte Ignace Mielzinsky, relatif à une larve dévore l'Helix nemoralis. Annales des Sciences Naturelles 2: 78–80.

Magis, N. 1977. Catalogue des Coléoptères de Belgique. Fascicule VI. Catalogue raisonne des Cantharoidea. Premiere Partie. Homalisidae, Drilidae, Lampyridae et Lycidae. Société Royale Belge d'Entomologie, Brussels, 60 pp.

Mielzinsky, I. 1824. Mémoire sur une larve qui dévore les Helix nemoralis, et sur l'insecte auquel elle donne naissance. Annales des Sciences Naturelles 2: 67–77, pl. 15, figs. 1–11.

Olivier, E. 1910. Pars 10. Rhagophthalmidae, Drilidae. IN: S. Schenkling (ed.), Coleopterorum Catalogus. W. Junk, Berlin, 10 pp.

Rosenberg, E. C. 1909. Bidrag til kundskaben om billernes udvikling, levevis og systematik. II. Drilus concolor Ahr.: hunnens forvandling i skallen af Helix hortensis. Entomologiske Meddelelser (2) 3: 227–240, 2 pls.

Wittmer, W. 1944. Catalogue des Drilidae E. Oliv. (Coleoptera-Malacodermata). Revista de la Sociedad Entomológica Argentina 12: 203–221.

General appearance. Total length 5–30 mm. Ratio of body length to greatest body width 3.85–4.85. Body slightly flattened to moderately convex. Sides of body not evenly curved. Body not capable of conglobation (rolling into a ball). Upper surfaces of body clothed with distinct hairs, setae or scales. Vestiture of upper surfaces not including stiff, erect, dark bristles; not including scales or scale-like setae. Upper surfaces of body without deep foveae. Prothorax, metathorax and-or abdomen without extrusible glands. Underside of body without hydrofuge surface(s).

Head. Ratio of head length to its greatest width (excluding eyes) 1 or less. Head width just behind eyes not distinctly greater than prothoracic width. Head not or slightly declined; not entirely concealed from above by pronotum; without elongate rostrum; not abruptly constricted posteriorly. Temples absent or not closely adpressed to prothorax; absent. Transverse occipital ridge or carina absent. Occiput without stridulatory file. Longitudinal axis of head (from occipital foramen to mouth cavity) inclined at an angle of less than 45 degrees. Frontal region not to moderately, gradually declined. Occipital region without median longitudinal groove or line (endocarina). Frontal region without median groove or line (endocarina). Head without ocelli.

Compound eyes present. Eyes not or only slightly protuberant. Vertical diameter of eye less than 2 times horizontal diameter. Eyes finely facetted; without interfacetal setae. Ommatidium of the exocone type (?). Eye entire. Anterior or mesal edge of eye not or only barely emarginate. Posterior edge of eye not or barely emarginate.

Antennal insertions exposed from above; moderately to widely separated. Antennae not borne on raised tubercles. Antennal insertions flush with head capsule or raised, not in fossae. Subantennal groove or cavity on head absent or very weakly developed. Frontoclypeal suture absent or incomplete. Clypeus not laterally emarginate. Anterior edge of clypeus or clypeolabrum straight to convex. Mouth cavity anteriorly or anteroventrally oriented. Pregular area without laterally opening cavities. Head ventrally without paired subgenal ridges. Head without anteriorly-projecting genal processes. Gular sutures widely separated or absent. Corporotentorium incomplete or absent. Cervical sclerites present.

Antennae. Number of antennomeres 10, or 11. Antennae when posteriorly extended reaching beyond middle of prothorax but not middle of elytra. Antennae moniliform, or serrate. Antennomeres 3, 4 or 5 to 10 without or with single rami (uniramose). Antennae at least partly pubescent or with obvious modifications. Antennal modifications beginning on antennomere 3 (rarely 2), or antennomere 4. First antennomere (scape) less than 3 times as long as 2nd (pedicel). Antenna not geniculate; without apical club.

Mouthparts. Labrum at least partly visible; partly or completely fused to clypeus or frontoclypeus, without or with incomplete suture (?). Major portion of labrum strongly transverse. Apex of labrum subtruncate to slightly convex. Labrum mostly membranous or very lightly sclerotized. Mouthparts not forming a piercing or sucking tube. Mandibles present. Mandible very narrow and elongate. Mandibular apex moderately to strongly, gradually curved mesally; unidentate, truncate or rounded; subacute, bidentate or multidentate. Dorsal part of mandible without tubercle; without setose cavity. Mandible moderately to strongly, more or less evenly sclerotized or pigmented; visible in lateral view. Incisor edge of mandible with single tooth. Mandible without mola; without prostheca. Prostheca absent or without articulated, sclerotized process. Inner basal angle of mandible without pubescent process. Maxilla with distinct galea and lacinia. Maxillary lobe(s) not stylet-like. Apex of galea or maxillary lobe densely setose or spinose; without heavily sclerotized teeth or hooks. Lacinia without hook(s) or spine(s). Apical maxillary palpomere cylindrical to fusiform; at least as wide as or longer than preapical one. Maxillary palp without complex palp organ. Apical labial palpomere cylindrical to fusiform. Ligula undivided or finely cleft.

Prothorax. Ratio of pronotal length to greatest pronotal width 0.47–0.62. Prothorax widest at middle. Sides of prothorax moderately to strongly curved, or straight posteriorly, curved anteriorly. Prothorax not laterally compressed to form cavities for legs. Sides of prothorax not or slightly explanate. Base of prothorax not or slightly narrower than elytral bases. Greatest prothoracic width not or slightly narrower than greatest elytral width. Lateral pronotal carinae absent. Lateral portion of prothorax without deep pit. Pronotum without anterolateral callosities. Anterior angles of pronotum absent or not produced forward; absent, right or rounded, not produced. Posterior angles of pronotum absent or broadly rounded; not produced and acute. Posterior edge of pronotum more or less straight or evenly rounded; simple; not or vaguely margined. Discal carinae of pronotum absent. Pronotal disc without paired basal impressions. Pronotum without median longitudinal groove or line. Anterior edge of pronotum simple, without margin. Hypomeron without pit.

Lateral portion of prosternum in front of coxae shorter than mid length of procoxal cavity. Anterior edge of prosternum not produced anteriorly. Prosternum in front of coxae flat to moderately convex. Prosternum in front of coxae without paired lines or carinae. Anterior edge of prosternum without margin; without mesal excavation. Anterolateral or ventrolateral portions of prothorax without cavities or grooves. Prothoracic cavities absent. Prothoracic grooves absent. Prosternal process absent. Ventral portion of prothorax on each side with notosternal suture only. Propleuron not extending to anterior edge of prothorax. Propleuron or pleurotrochantin not extending behind coxa. Procoxae projecting well below prosternum. Procoxa without or with short concealed lateral extension. Procoxal cavities absent, procoxae attached externally. Postcoxal projection absent or very short. Prothoracic trochantin or pleurotrochantin at least partly exposed. Promesothoracic clicking mechanism absent.

Elytra. Elytra absent (anelytrous or larviform).

Pterothorax. Scutellum absent or not visible. Mesoventrite without paired procoxal rests. Paired mesoventral procoxal rests absent, horizontal or slightly oblique. Anterior edge of mesoventrite without prosternal rest. Mesoventrite not divided by longitudinal groove or discrimen. Anterior edge of mesoventrite at midline on same plane as metaventrite. Mesoventral cavity absent. Mesocoxa conical and projecting. Mesocoxal cavities absent, mesocoxae attached externally. Mesoventrite partly or completely fused to mesepisterna. Mesepisterna without deep pockets.

Metaventral discrimen or median line absent. Paired postcoxal lines of metaventrite absent. Postcoxal lines of metaventrite absent. Metaventrite not longer than first abdominal ventrite. Postcoxal pits of metaventrite absent. Metaventrite flat to slightly convex. Transverse groove of metaventrite absent. Anterior edge of metaventrite without transverse carina between mesocoxal cavities. Metacoxae widely separated; separated by more than 1 but less than 2 times longest coxal diameter, or separated by more than 2 times longest coxal diameter; not extending laterally to meet elytra or sides of body; completely separated from metaventrite by suture. Metacoxal plates absent. Metacoxae not greatly enlarged; horizontally oriented. Apical portion of metendosternite not or only slightly emarginate.

Hind wing. Hind wing highly reduced or absent.

Legs. Femoral attachment of mid trochanter transverse or slightly oblique. Mesotrochanter not reduced or concealed from below. Metafemur not much wider than mesofemur. Mesotibia not strongly widened. Outer edge of mesotibia simple, crenulate or denticulate. Outer subapical edge of mesotibia without antenna cleaner. Preapical surfaces of mesotibia without ridges or combs. Outer apical angle of mesotibia simple or slightly produced, without lobe, teeth or spines. Inner apical angle of mesotibia not or slightly produced, without tooth. Mesotibial spurs glabrous or absent; absent. Mesotarsus with 5 distinct tarsomeres (pentamerous). Tarsomeres on hind leg at least as many as on mid leg. Tarsomeres on fore leg at least as many as on mid leg. Mesotarsomere 1 well developed and visible. Preapical mesotarsomeres together longer than apical one. Penultimate mesotarsomere not distinctly shorter than antepenultimate. Ventral mesotarsal lobes absent. Mesotarsal claws paired; subequal in length and similar in form and angle of inclination; simple. Appendage on each tarsal claw absent. Mesotarsal claws with one or more setae near base. Mesotarsal empodium absent or concealed; absent or with 2 or fewer setae. Outer edge of protibia simple and rounded to carinate but without lobes or teeth, except at apex. Outer apical angle of protibia simple or slightly produced, without lobe, teeth or spines. Inner subapical edge of protibia without antenna cleaner. Protibial spurs absent. Hind legs without swimming hairs. Preapical surfaces of metatibia without ridges or combs. Metatibial articular area not to only moderately expanded, narrowly oval or oblique. Metatibial spurs absent.

Abdomen. Number of abdominal ventrites 9. Number of basal ventrites connate none. Abdominal sternite 2 visible. First ventrite not completely divided by metacoxae. Suture between ventrites 1 and 2 distinct. Suture between ventrites 2 and 3 distinct. Ventrite 4 articulated with or connate with both 3 and 5. Postcoxal lines on ventrite 1 absent. Ventrite 1 not much longer than 2. Abdominal process absent. Ventrite 5 in female without circular depression. Posterior edge of ventrite 5 not crenulate. Last visible tergite and-or sternite (7 or 8) not forming terminal spine. Tergite and sternite 7 separated by membrane or distinct suture. Subapical abdominal luminous organ absent. Ventrites without setose patches or foveae. Functional spiracles on abdominal segment 8 present. Functional spiracles on abdominal segment 7 present. Functional spiracles on abdominal segment 6 present. Functional spiracles on abdominal segment 5 present. 7th abdominal spiracles located in pleural membrane. 6th abdominal spiracles located in pleural membrane. 5th abdominal spiracles located in pleural membrane. Pygidium (sclerotized tergite 7 or 8) more or less horizontal.

Illustrations. • Drilus. Drilus concolor Ahrens. Locality: Denmark. Artist: Victor Hansen. Courtesy of Danmarks Fauna and Zoological Museum, University of Copenhagen. Reference: Hansen 1973.


The interactive key provides access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, and summaries of attributes within groups of taxa.

Cite this publication as: ‘Lawrence, J.F., Hastings, A.M., Dallwitz, M.J., Paine, T.A., and Zurcher, E.J. 2000 onwards. Elateriformia (Coleoptera): descriptions, illustrations, identification, and information retrieval for families and subfamilies. Version: 9th October 2005. http://delta-intkey.com’.

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