Elateriformia (Coleoptera)

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

ELMIDAE

(= Elmididae, Elminthidae, Helminthidae, Limniidae).

Classification. Polyphaga: Elateriformia.

Distribution. The Elmidae are more or less cosmopolitan in distribution, occurring wherever there are appropriate types of freshwater habitats.

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

Biology. Adult Elminae are are fully aquatic as adults and larvae, usually occurring in sand, gravel, or submerged wood in streams. Some feed on algae and detritus, while others attack woody surfaces, making them more suitable for further breakdown by microorganisms and other aquatic invertebrates (McKie and Cranston 1998). Many laraine adults are also aquatic, but but those of Lara, Phanocerus and some other genera occur in riparian situations and enter the water only for oviposition. Adults of all Elminae and some Larainae have a ventral plastron consisting of fine hydrofuge hairs.

References

Boukal, D. S. 1997. A revision of the genus Austrolimnius Carter & Zeck, 1929 (Insecta: Coleoptera: Elmidae) from New Guinea and the Moluccas. Annalen des Naturhistorischen Museums in Wien 99B: 155–215.

Brown, H. P. 1981. A distributional survey of the world genera of aquatic dryopoid beetles (Coleoptera: Dryopidae, Elmidae, and Psephenidae sens. lat.). Pan-Pacific Entomologist, 57: 133–148.

Brown, H. P. 1981. Key to the world genera of Larinae (Coleoptera, Dryopoidea, Elmidae), with descriptions of new genera from Hispaniola, Colombia, Australia, and New Guinea. Pan-Pacific Entomologist, 57: 76–104.

Brown, H. P. 1991. Elmidae (Dryopoidea), pp. 404–407. IN: F. W. Stehr (ed.), Immature Insects. Vol. 2. Kendall/Hunt Publishing Co., Dubuque, Iowa.

Carter, H. J. and E. H. Zeck 1929. A monograph of the Australian Dryopidae. Order-Coleoptera. Australian Zoologist 6: 49–72, pls. i-vii.

Ciampor, F. and J. Kodada 1998. Elmidae: I. Taxonomic revision of the genus Macronychus Müller (Coleoptera), pp. 219–287. IN: M. A. Jäch and L. Ji (eds.), Water Beetles of China. Vol. II. Zoologisch-Botanische Gesellschaft in Österreich und Wiener Coleopterologenverein, Vienna.

Hinton, H. E. 1939. An inquiry into the natural classification of the Dryopoidea, based partly on a study of their internal anatomy. Transactions of the Royal Entomological Society of London, 87: 133–184,

Hinton, H. E. 1939. On some new genera and species of neotropical Dryopoidea (Coleoptera). Transactions of the Royal Entomological Society of London, 89: 23–46.

Hinton, H. E. 1940. A monographic revision of the Mexican water beetles of the family Elmidae. Novitates Zoologicae, London, 42: 217–396.

Hinton, H. E. 1968. The subgenera of Austrolimnius (Coleoptera: Elminthidae). Proceedings of the Royal Entomological Society of London (B) 37: 98–102, 1 pl.

Hinton, H. E. 1971. The species of Dryopomorphus (Coleoptera, Elmidae). Entomologist, 104: 293–297, pl. 5.

Jäch, M. A. 1997. Description of Laorina, a new laraine genus from Laos (Coleoptera Elmidae). Tropical Zoology 10: 393–398.

Jäch, M. A. and D. Boukal 1995. Elmidae: 2. Notes on Macronychini, with description of four new genera from China, pp. 299–324. IN: M. A. Jäch and L. Ji (eds.), Water Beetles of China. Vol. I. Zoologisch-Botanische Gesellschaft in Österreich und Wiener Coleopterologenverein, Vienna.

Jäch, M. A. and J. Kodada 1995. Elmidae: 1. Check list and bibliography of the Elmidae of China, pp. 289–298. IN: M. A. Jäch and L. Ji (eds.), Water Beetles of China. Vol. I. Zoologisch-Botanische Gesellschaft in Österreich und Wiener Coleopterologenverein, Vienna.

Kodada, J. 1993. Jaechomorphus, a new riffle beetle genus from Sumatra (Coleoptera: Elmidae: Larainae). Entomological Problems 24(2): 1–17.

McKie, B. G. L. and P. S. Cranston 1998. Keystone coleopterans? Colonization by wood-feeding elmids of experimentally immersed woods in south-eastern Australia. Marine and Freshwater Research 49: 79–88.

Olmi, M. 1976. Fauna d'Italia, XII. Coleoptera: Dryopidae, Elminthidae. Edizioni Calderini, Bologna. vii + 280 pp.

Shepard, W. 2000. 47. Elmidae. IN: R. H. Arnett, Jr., Jr. and M. C. Thomas (eds.), American Beetles. CRC Press, Gainesville, Florida (in press).

Spangler, P. J. and H. P. Brown. 1981. The discovery of Hydora, a hitherto Australia-New Zealand genus of riffle beetles, in Austral South America (Coleoptera: Elmidae). Proceedings of the Entomological Society of Washington, 83: 596–606.

Spangler, P. J. and S. Santiago-Fragoso. 1992. The aquatic beetle subfamily Larainae (Coleoptera: Elmidae) in Mexico, Central America, and the West Indies. Smithsonian Contributions to Zoology, 528: 1–74.

Steffan, A. W. 1961. Vergleichend-mikromorphologische Genitaluntersuchungen zur Klärung der phylogenetischen Verwandtschaftsverhältnisse der mitteleuropäischen Dryopoidea (Coleoptera). Zoologische Jahrbücher, Abteilung für Systematik, Ökologie und Geographie der Tiere, 88: 255–354.

Steffan, A. W. 1979. 42. Familie: Dryopidae, pp. 265–294. IN: H. Freude, K. W. Harde and G. A. Lohse (eds.), Die Käfer Mitteleuropas. Band 6. Diversicornia. Goecke & Evers, Krefeld.

Stride, G. O. 1955. On the respiration of an aquatic African beetle, Potamodytes tuberosus Hinton. Annals of the Entomological Society of America 48: 344–351.

Zaitzev, P. 1910. Pars 17. Dryopidae, Cyathoceridae, Georyssidae, Heteroceridae. IN: S. Schenkling (ed.), Coleopterorum Catalogus. W. Junk, Berlin, 68 pp.

General appearance. Total length 0.9–10.2 mm. Ratio of body length to greatest body width 1.8–3.1. 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 glabrous or subglabrous, or 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), or with 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. 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. 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, or strongly protuberant. Vertical diameter of eye less than 2 times horizontal diameter. Eyes finely facetted, or coarsely 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, or narrowly 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 distinctly impressed; straight, slightly curved or angulate. 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 broad, or narrow; without median process. Cervical sclerites present.

Antennae. Number of antennomeres 7–10, or 11. Antennae when posteriorly extended not reaching middle of prothorax, or reaching beyond middle of prothorax but not middle of elytra. Antennae filiform, or serrate, or incrassate or clavate, or capitate. Antennomeres 3, 4 or 5 to 10 without or with single rami (uniramose). Antennae entirely subglabrous and without obvious modifications, or at least partly pubescent or with obvious modifications. Antennal modifications beginning on 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; without apical club, or with weak apical club, or with strong apical club. Antennal club 1-segmented, or 5-segmented, or with 6 or more segments; not 5-segmented or with 2nd segment subequal to or larger than 1st; loose, or compact; not lamellate; not or slightly serrate; not cupuliform; not or slightly flattened; not preceded by a cupule.

Mouthparts. Labrum at least partly visible; free, membranous or separated by suture. Major portion of labrum strongly transverse, or slightly transverse or subquadrate. Apex of labrum subtruncate to slightly convex, or slightly concave or emarginate. Labrum moderately to heavily sclerotized, except at base and-or apex. Mouthparts not forming a piercing or sucking tube. Mandibles present. Mandible short and broad. Mandibular apex moderately to strongly, gradually curved mesally; bidentate or bilobed, or multidentate or multilobed; 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 with well developed mola; with well developed 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, 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, or slightly to strongly expanded apically. Ligula undivided or finely cleft.

Prothorax. Ratio of pronotal length to greatest pronotal width 0.6–1.1. Prothorax widest 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, or distinctly narrower than elytral bases. Greatest prothoracic width not or slightly narrower than greatest elytral width, or distinctly narrower than greatest elytral width. Lateral pronotal carinae complete, or incomplete, or absent; simple; visible for their entire lengths from above, or not visible for their entire length from above; without a raised margin, or 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, or distinctly produced forward; absent, right or rounded, not produced, or produced and broadly rounded or obtusely angulate, or produced and narrowly rounded or acute. Posterior angles of pronotum obtuse or right, or moderately to strongly acute; not produced and acute. Posterior edge of pronotum more or less straight or evenly rounded, or distinctly sinuate or variously lobed; simple; not or vaguely margined. Discal carinae of pronotum absent, or basal but mesad of posterior angles, or extending beyond middle of disc. Pronotal disc without paired basal impressions, or with paired basal impressions. Pronotum without median longitudinal groove or line. Anterior edge of pronotum simple, without margin. 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 shorter than mid length of procoxal cavity, or as long as mid length of procoxal cavity, or 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, or with 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 complete; narrowed apically, or parallel-sided; flat, concave, or only slightly elevated or curved behind coxae, or slightly to strongly elevated but not curved behind; slightly overlapping mesoventrite, or moderately to strongly overlapping mesoventrite. Apex of prosternal process acute or narrowly rounded, or broadly rounded, angulate or truncate. 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, or projecting well below prosternum. Procoxa without or with short concealed lateral extension, or with long concealed, lateral extension. Procoxal cavities present, procoxae countersunk. Procoxal cavity strongly transverse, or slightly transverse, or circular or longer than wide. Procoxal cavities at middle moderately to widely separated. Procoxal cavities externally open; broadly open. Postcoxal projection absent or very short. Procoxal cavities without narrow lateral extensions. Procoxal cavities internally open. Prothoracic trochantin or pleurotrochantin at least partly exposed, or completely concealed or absent. Promesothoracic clicking mechanism absent.

Elytra. Elytra present. Ratio of elytral length to greatest elytral width 1.3–2.5. Ratio of elytral length to pronotal length 1.8–4.7. Elytra apunctate, irregularly punctate, or with 5 or fewer distinct puncture rows or striae, or with more than 5 distinct puncture rows, or with more than 5 distinct impressed striae; without scutellary striole, or with scutellary striole. Number elytral puncture rows or striae 10, or 9, or 8 or fewer. 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. Mesoscutum without stridulatory file. Mesoventrite with paired procoxal rests. Paired mesoventral procoxal rests absent, horizontal or slightly oblique, or moderately to strongly oblique, or vertical. Anterior edge of mesoventrite without prosternal rest. Mesoventrite not divided by longitudinal groove or discrimen, or at least partly divided by longitudinal groove or discrimen. Anterior edge of mesoventrite at midline on same plane as metaventrite. Mesoventral cavity absent, or small and shallow, or moderately large and shallow, or moderately to very large and deep. Mesocoxa not conical and projecting, or conical and projecting. Mesocoxal cavities present, mesocoxae countersunk. 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 absent or not extending to middle of mesocoxal cavity, or extending at least to middle of mesocoxal cavity. Mesometaventral junction a straight line, or a complex fitting. Mesoventral and metaventral processes at midline separated by gap, groove, or suture.

Metaventral discrimen or median line moderately to very long. Paired postcoxal lines of metaventrite absent. Postcoxal lines of metaventrite absent. 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 present. 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, or widely separated; separated by less than longest coxal diameter; not extending laterally to meet elytra or sides of body, or 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, or absent; 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, or short or absent. Anterior tendons of metendosternite moderately or very close together, or widely separated but not on lateral arms. Apical portion of metendosternite not or only slightly emarginate.

Hind wing. Hind wing well developed, or highly reduced or absent; with normal transverse folds. Radial cell of hind wing well developed, or highly reduced or absent; elongate, or shorter and broader, or incomplete or absent. Inner posterior angle formed at base of radial cell right or obtuse, or acute. Radial cell not forming equilateral triangle. Ratio of length of apical area to total wing length 0.20–0.35, or 0.36–0.5. Apical area of hind wing with one or more distinct veins (branches of RA and-or RP). Medial bar of hind wing not crossed by fold. Free veins in medial area of hind wing 5 or 6, or 4, or 3 or fewer. 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. Anal lobe of hind wing absent. Posterior edge of hind wing without fringe of long hairs.

Legs. Femoral attachment of mid trochanter 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. 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. 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, or shorter 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, or toothed or bifid. Appendage on each tarsal claw absent. Mesotarsal claws without setae near base. Mesotarsal empodium 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. 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.

Abdomen. Number of abdominal ventrites 5, or 6. Number of basal ventrites connate three. 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, or 1 pair, straight or slightly curved. Ventrite 1 not much longer than 2. Abdominal process acute or narrowly rounded, or broadly rounded or angulate, or truncate or slightly emarginate, or 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, or absent. Anterior edge of sternite 8 in male without median strut, or with median strut. Pygidium (sclerotized tergite 7 or 8) more or less horizontal. Anterior edge of sternite 9 in male without median strut, or with median strut (spiculum gastrale). Tergite 9 in male truncate, or slightly to moderately emarginate, or almost completely divided into two parts, or completely fused to tergite 10. Tergite 10 in male well developed and free, or partly fused to tergite 9, or completely membranous or fused to tergite 9.

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, or with dorsal and ventral lobes. Anterior edge of penis without struts, or with paired struts.

Illustrations. • Austrolimnius. Austrolimnius waterhousei Hinton. Locality: Australia. Artist: F. Nanninga. Copyright CSIRO. Reference: Britton 1970. • Disersus. Disersus longipennis Sharp. Locality: Central America. Reference: Sharp 1882. • Jaechomorphus. Jaechomorphus gracilis Kodada. Locality: Sumatra. Artist: D. Matichová. Courtesy of Entomological Problems. Reference: Kodada 1993.


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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