Elateriformia (Coleoptera)

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

EUCNEMIDAE (major part)

(= Melasidae).

Classification. Polyphaga: Elateriformia.

Distribution. Eucnemidae occur in all major regions of the world, although many taxa are rare in collections.

Biogeographic regions: Nearctic, Palearctic, Neotropical, Afrotropical, Oriental, Australian.

Biology. Adult Eucnemidae are usually collected on plant surfaces, at lights at night, or in flight-intercept traps. Larvae of most taxa occur in dead wood and are capable of moving through fairly solid wood by forcing their bodies between wood fibers; however some are soil-dwelling (see Phyllocerini and Perothopinae). Eucnemid larvae are liquid feeders, so their actual diet is difficult to ascertain. It is possible that they feed on the plasmodium of Myxomycetes, or digest plant tissue extra-orally.

References

Bonvouloir, H. 1871. Monographie de la famille des Eucnémides (part 1). Annales de la Société Entomologique de France (4) 10, Partie Supplémentaire, pp. 1–288, pls. 1–21.

Bonvouloir, H. 1872. Monographie de la famille des Eucnémides (part 2). Annales de la Société Entomologique de France (4) 10, Partie Supplémentaire, pp. 289–560, pls. 22–36.

Bonvouloir, H. 1875. Monographie de la famille des Eucnémides (parts 3 & 4). Annales de la Société Entomologique de France (4) 10, Partie Supplémentaire, pp. 561–907, pls. 37–42.

Burakowski, B. 1989. Hypermetamorphosis of Rhacopus attenuatus (Maeklin) (Coleoptera, Eucnemidae). Annales Zoologici (Warszawa) 42: 165–180.

Burakowski, B. 1991. Klucze do Oznaczania Owadow Polski. XIX. Coleoptera. 35–37. Cerophytidae, Eucnemidae, Throscidae, Lissomidae. Polskie Towarzystwo Entomologiczne, Wroclaw, 91 pp,

Cobos, A. 1964. Materiales para el estudio de la familia Eucnemidae. Primera parte. Eos, Madrid 40: 289–435.

Ford, E. J. and T. J. Spilman 1979. Biology and immature stages of Dirrhagofarsus lewisi, a species new to the United States (Coleoptera, Eucnemidae). Coleopterists Bulletin 33: 75–83.

Fleutiaux, E. 1902. Essai d'une classification de Melasidae (Eucnemidae des auteurs). Annales de la Société Entomologique de France 70: 636–664.

Fleutiaux, E. 1920. Études sur les Melasidae (Coleoptera-Serricornia). Première partie. Annales de la Société Entomologique de Belgique 60: 93–104.

Fleutiaux, E. 1921. Études sur les Melasidae (Coleoptera-Serricornia). (Parts 2–9). Annales de la Société Entomologique de Belgique 61: 23–41, 68–87, 91–108, 124–145, 169–192, 223–242, 281–309, 383–387.

Gardner, J. C. M. 1935. Immature stages of Indian Coleoptera (17) (Eucnemidae). Indian Forest Records. New Series (Entomology) 1: 79–94.

Lohse, G. A. 1979. 36. Familie: Eucnemidae, pp. 187–201. IN: H. Freude, K. W. Harde and G. A. Lohse (eds.), Die Käfer Mitteleuropas. Band 6. Diversicornia. Goecke & Evers, Krefeld.

Lucht, W. 1981. Die Präimaginalstadien von Hypocoelus olexai Palm (Col., Eucnemidae) nebst Bestimmungstabelle der Larven nord- und mitteleuropäischer Hypocoelus-Arten. Entomologische Blätter 77: 61–74.

Mamaev, B. M. 1976. Morphological types of eucnemid larvae (Coleoptera, Eucnemidae) and their evolutionary significance, pp. 136–155. IN: B. M. Mamaev (ed.), Evolutionary Morphology of Insect Larvae. "Nauka", Moscow (in Russian).

Muona, J. 1987. The generic names of the beetle family Eucnemidae (Coleoptera). Entomologica Scandinavica 18: 79–92.

Muona, J. 1991. A revision of the Indomalesian tribe Galbitini new tribe (Coleoptera, Eucnemidae). Entomologica Scandinavica, Supplement 39: 67 pp.

Muona, J. 1993. Eucnemidae and Throscidae from Baltic amber (Coleoptera). Entomologische Blätter 89: 15–45.

Muona, J. 1993. Review of the phylogeny, classification and biology of the family Eucnemidae (Coleoptera). Entomologica Scandinavica, Supplement No. 44: 133 pp.

Muona, J. 1995. The phylogeny of Elateroidea (Coleoptera), or which tree is best today? Cladistics 11: 317–341.

Muona, J. 2000. A Revision of the Nearctic Eucnemidae (Coleoptera). Acta Zoologica Fennica (in press).

Muona, J. 2000. 61. Eucnemidae. IN: R. H. Arnett, Jr., Jr. and M. C. Thomas (eds.), American Beetles. CRC Press, Gainesville, Florida (in press).

Schenkling, S. 1928. Pars 96. Melasidae. IN: S. Schenkling (ed.), Coleopterorum Catalogus. W. Junk, Berlin, 110 pp.

General appearance. Total length 2–25 mm. Ratio of body length to greatest body width 2.4–3.6. Body slightly flattened to moderately convex, or strongly 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) greater than 1, or 1 or less. Head width just behind eyes not distinctly greater than prothoracic width. Head not or slightly declined, or moderately to strongly 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, or present. Occiput without stridulatory file. Longitudinal axis of head (from occipital foramen to mouth cavity) inclined at an angle of less than 45 degrees, or inclined at an angle of 45 to 90 degrees, or inclined at an angle of more than 90 degrees. Frontal region not to moderately, gradually declined, or strongly deflexed, vertical or inflexed at apex only. Occipital region without median longitudinal groove or line (endocarina). Frontal region without median groove or line (endocarina), or with median groove or line (endocarina). Head without ocelli.

Compound eyes present. Eyes not or only slightly protuberant, or strongly protuberant. Vertical diameter of eye less than 2 times horizontal diameter. Eyes finely facetted; without interfacetal setae. Ommatidium of the eucone type, or of the acone 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, or narrowly separated, or closely approximate or contiguous. Antennae not borne on raised tubercles. Antennal insertions flush with head capsule or raised, not in fossae, or countersunk so that they lie within saucer-like fossae. Subantennal groove or cavity on head absent or very weakly developed, or well developed. Frontoclypeal suture absent or incomplete. Clypeus not laterally emarginate. Anterior edge of clypeus or clypeolabrum straight to convex, or concave to shallowly emarginate, or deeply emarginate or excavate, or complexly lobed or dentate. Mouth cavity anteriorly or anteroventrally oriented, or ventrally or posteroventrally oriented. Pregular area without laterally opening cavities. Head ventrally without paired subgenal ridges, or with 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 11. Antennae when posteriorly extended reaching beyond middle of prothorax but not middle of elytra. Antennae filiform, or moniliform, or serrate, or pectinate or bipectinate, or flabellate or biflabellate, or incrassate or clavate, or capitate. 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, or antennomere 5, or antennomere 5 or beyond. First antennomere (scape) less than 3 times as long as 2nd (pedicel), or more than 3 times as long as 2nd (pedicel). Antenna not geniculate, or geniculate or elbowed; without apical club, or with weak apical club, or with strong apical club. Antennal club 3-segmented, or with 6 or more segments; not 5-segmented or with 2nd segment subequal to or larger than 1st; loose; not lamellate; not or slightly serrate, or strongly serrate or pectinate, or flabellate; not cupuliform; not or slightly flattened, or distinctly flattened; not preceded by a cupule.

Mouthparts. Labrum concealed beneath clypeus or apparently absent; free, membranous or separated by suture. Major portion of labrum strongly transverse. Apex of labrum subtruncate to slightly convex, or slightly concave or emarginate, or deeply emarginate or bilobed. Labrum moderately to heavily sclerotized, except at base and-or apex, or mostly membranous or very lightly sclerotized. Mouthparts not forming a piercing or sucking tube. Mandibles present. Mandible short and broad, or moderately elongate. Mandibular apex not or slightly and gradually curved mesally, or moderately to strongly, gradually curved mesally; unidentate, truncate or rounded, or bidentate or bilobed; 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 simple, or with single tooth. Mandible without mola; without prostheca. Inner basal angle of mandible without pubescent process. Maxilla with distinct galea and lacinia, or with single apical lobe. Maxillary lobe(s) not stylet-like. Apex of galea or maxillary lobe densely setose or spinose, or without or with few setae or spines; without heavily sclerotized teeth or hooks. Lacinia without hook(s) or spine(s). Apical maxillary palpomere cylindrical to fusiform, or slightly expanded and truncate to subtriangular, or securiform to cultriform; 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, or shallowly to moderately emarginate.

Prothorax. Ratio of pronotal length to greatest pronotal width 0.48–1. Prothorax widest anteriorly, or at middle, or posteriorly. Sides of prothorax more or less straight, or straight posteriorly, curved anteriorly, or sinuate. 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 complete; simple; visible for their entire lengths from above, or not visible for their entire length from above; with a raised margin or narrow bead. 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 moderately to strongly acute; strongly produced and narrowly acute. Posterior edge of pronotum distinctly sinuate or variously lobed; simple; not or vaguely margined. Discal carinae of pronotum absent, or located on posterior angles only. Pronotal disc without paired basal impressions, or with paired basal impressions. Pronotum without median longitudinal groove or line, or with median longitudinal groove or line. Anterior edge of pronotum simple, without margin, or with narrow margin or bead. Hypomeron without pit.

Anterior portion of prosternum at midline shorter than prosternal process, or as long as prosternal process, or longer than prosternal process. Lateral portion of prosternum in front of coxae longer than mid length of procoxal cavity. Anterior edge of prosternum not produced anteriorly, or distinctly produced forming chin piece. Prosternum in front of coxae flat to moderately convex, or strongly convex without carina. 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, or with broad cavities, or with narrow grooves. Prothoracic cavities absent, or external, open anteriorly, not visible from above. Prothoracic grooves absent, or longitudinal, below lateral edges of prothorax, or longitudinal or oblique, elsewhere on hypomera or prosternum. Prosternal process complete; narrowed apically, or parallel-sided; strongly elevated and curved dorsally behind coxae, or slightly to strongly elevated but not curved behind; moderately to strongly overlapping mesoventrite. Apex of prosternal process acute or narrowly rounded. Prosternal process without transverse groove. Accessory (mesal) procoxal articulation 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 not or slightly projecting below prosternum. Procoxa without or with short concealed lateral extension. Procoxal cavity circular or longer than wide. Procoxal cavities at middle moderately to widely separated. Procoxal cavities externally open; broadly open, or narrowly open. Postcoxal projection absent or very short, or moderately long but not meeting prosternal process. Procoxal cavities without narrow lateral extensions. Procoxal cavities internally open, or closed by slender bar. Prothoracic trochantin or pleurotrochantin completely concealed or absent. Promesothoracic clicking mechanism present.

Elytra. Elytra present. Ratio of elytral length to greatest elytral width 1.7–3. Ratio of elytral length to pronotal length 2.35–4.85. Elytra apunctate, irregularly punctate, or with 5 or fewer distinct puncture rows or striae, or with more than 5 distinct impressed striae; without scutellary striole. Number elytral puncture rows or striae 9. Sutural stria absent or not deeply impressed near apex. Abdominal tergites exposed by elytra none or apex of 1. Elytral apices meeting or almost meeting at the suture, or independently rounded or acute and separated by broad gap. Elytral suture not deflected near apex. Elytral apex without internal interlocking tongue. Epipleuron absent or incomplete, or complete; not or gradually narrowed. Lateral edge of elytron straight or weakly sinuate.

Pterothorax. Scutellum well developed; abruptly elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or truncate. Mesoscutum without stridulatory file. Mesoventrite with paired procoxal rests. Paired mesoventral procoxal rests absent, horizontal or slightly oblique, or moderately to strongly oblique. Anterior edge of mesoventrite without prosternal rest, or with median prosternal rest. Mesoventrite not divided by longitudinal groove or discrimen. Anterior edge of mesoventrite at midline on same plane as metaventrite, or on different plane than metaventrite. Mesoventral cavity moderately to very large and deep. Mesocoxa not conical and projecting. Mesocoxal cavities at middle moderately to widely separated. Mesocoxae separated by less than shortest diameter of coxal cavity, or more than shortest diameter of coxal cavity. Mesocoxal cavities circular to slightly transverse; not or slightly oblique. Mesoventrite separated by complete sutures from mesepisterna. Mesepisterna distinctly separated at midline; without deep pockets. Mesepimeron not visible from above. Mesocoxal cavities open laterally; not partly closed by metepisterna. Mesoventral process extending at least to middle of mesocoxal cavity. Mesometaventral junction a straight line, or an anteriorly curved, angulate or acute line, or a complex fitting. Mesoventral and metaventral processes at midline separated by gap, groove, or suture. Accessory (mesal) mesocoxal articulation absent.

Metaventral discrimen or median line moderately to very long, or short, or absent. Paired postcoxal lines of metaventrite absent, or present. Postcoxal lines of metaventrite absent, or arched and strongly recurved, or arched but not or slightly recurved, or straight or slightly, mesally curved. Metaventrite longer than first abdominal ventrite. Postcoxal pits of metaventrite absent. Metaventrite flat to slightly convex, or moderately to strongly convex. Transverse groove of metaventrite absent. Anterior edge of metaventrite without transverse carina between mesocoxal cavities. Exposed portion of metepisternum moderately elongate, or very long and narrow or absent. Metacoxae contiguous or narrowly separated; separated by less than longest coxal diameter; extending laterally to meet elytra or sides of body; completely separated from metaventrite by suture. Metacoxal plates well developed, more or less uniform, or well developed mesally, weak laterally, or weakly developed; not concealing most of basal abdominal ventrite. Metacoxae not greatly enlarged; horizontally oriented. Lateral arms of metendosternite short or absent. Metendosternal laminae absent. Ventrolateral processes of metendosternite absent or weakly developed, or strongly developed. Anterior process of metendosternite moderately long. Anterior tendons of metendosternite moderately or very close together. Apical portion of metendosternite not or only slightly emarginate.

Hind wing. Hind wing well developed; with normal transverse folds. Radial cell of hind wing well developed, or highly reduced or absent; elongate, or incomplete or absent. Inner posterior angle formed at base of radial cell right or obtuse. Radial cell not forming equilateral triangle. Ratio of length of apical area to total wing length less than 0.2, or 0.20–0.35. Apical area of hind wing without veins or sclerotizations, or with one or more vague sclerotizations or pigment patches. Medial bar of hind wing not crossed by fold. Free veins in medial area of hind wing 5 or 6, or 4. Oblongum cell of hind wing absent. Medial fleck of hind wing absent; absent or not partly bisected by a vein. Wedge cell of hind wing well developed, or reduced, or absent. Apex of wedge cell of hind wing squarely truncate, or obliquely truncate, or acute. Anal lobe of hind wing absent, or present. Posterior edge of hind wing without fringe of long hairs.

Legs. Femoral attachment of mid trochanter transverse or slightly oblique, or strongly oblique with base of femur separate from coxa. 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, or with distinct teeth or long spines. Outer subapical edge of mesotibia without antenna cleaner. Preapical surfaces of mesotibia without ridges or combs, or with transverse or oblique 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; double, or 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, or on penultimate tarsomere only, or on more than one tarsomere. Mesotarsal claws paired; subequal in length and similar in form and angle of inclination; simple, or toothed or bifid. Appendage on each tarsal claw absent. Mesotarsal claws without setae near base. Mesotarsal empodium present and exposed, or 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 double, or single, or absent. Articulations of protibial spurs located in same plane. 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 double, or absent; subequal in length and form.

Abdomen. Number of abdominal ventrites 5. Number of basal ventrites connate five or six. Abdominal sternite 2 apparently absent. 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 acute or narrowly rounded. 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, or with 1 or more setose patches. 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. Anterior edge of sternite 8 in male without median strut. Pygidium (sclerotized tergite 7 or 8) more or less horizontal. Anterior edge of sternite 9 in male without median strut. Tergite 9 in male truncate, or slightly to moderately emarginate. Tergite 10 in male well developed and free.

Aedeagus trilobate; symmetrical, or asymmetrical. Anterior edge of tegmen or phallobase without struts. Parameres individually articulated to phallobase or base of penis, or partly or entirely fused together but articulated to phallobase; not outwardly hooked. Penis without dorsal and ventral lobes. Anterior edge of penis without struts, or with paired struts.

Illustrations. • Euryptychus. Euryptychus porosus (Lea). Locality: Australia. Artist: F. Nanninga. Copyright CSIRO. Reference: Britton 1970.


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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