British insects: the families of Coleoptera
British insects: the families of Coleoptera | |
Including Cebrionidae, Cavicoxumidae, Dicronychidae, Lissomidae, Throscidae part.
Click-beetles, Skip-jack beetles, Wire-worms.
General appearance. 2.8–30 mm long (?). Body length/maximum body width 1.73–5.16. Elytral length/pronotal length 1.3–6. Base of prothorax not or scarcely narrower than the combined elytral bases, or distinctly narrower than the combined elytral bases. Greatest prothoracic width not narrower or only slightly narrower than the greatest elytral width, or distinctly narrower than greatest elytral width. Beetles elongate to slender; not necked; not waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae.
Detailed morphology. Beetles clicking and ‘jumping’ to right themselves when inverted (flexing violently at the junction of the pro- and mesothorax). Inclination of the head slight to very strong. Eyes strongly protuberant, or not strongly protuberant; without bristles; finely facetted. The frons with a transverse ridge between the eyes. The labrum externally visible from above. Antennae short to long, but not exceeding the insect’s head to tail length; 11(–12) segmented. Antennal scape not swollen. Antennae filiform, or serrate, or pectinate (occasionally plumose). Antennal insertions visible from above, or hidden from above; ‘countersunk’ within saucer-like fossae, or not in fossae. Mandibular prosthecae well developed to absent. Prothorax shorter than wide to longer than wide. Pronotal length/maximum pronotal width 0.4–1.35. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. The scutellum elevated, or not elevated. Metaventrite without a transverse groove. Hind coxae contiguous, posteriorly shaped to receive the retracted femur (with transverse cavities). Tarsal segmentation formula 5, 5, 5. The tarsi usually without bilobed segments; without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous. The claws of the mid-leg tarsi not appendaged (but sometimes with basal setae). The claws of the mid-leg tarsi simple, or one-toothed or bifid, or serrate, denticulate or pectinate; with an empodium between them (this sometimes with three or more setae). Hind tarsi with as many segments as the mid-tarsi; 5-segmented. Elytral length/maximum width across the elytra 1–3.83. Elytra exposing no more than part of the terminal tergite to at least three complete abdominal tergites; hard. Scutellary striole absent. Wings well developed, or absent or much reduced. Exposed abdominal sternites 5; comprising both fused and movable components; immovably joined 2–4 (segment 5 being movable). Abdominal segment 8 with apparently functional spiracles.
Adult habitat, ecology. Predacious, or not predacious; in living vegetation.
Larvae. Larvae predacious, or not predacious; when non-predacious, phytophagous; on living vegetation (commonly in plant roots, including pests familiar as ‘wireworms’ in grass and root crops). The larvae wiry-bodied, with the labrum absent or fused to the clypeus, and abdominal segment 9 conical.
Classification. Suborder Polyphaga; Infraorder Elateriformia; Superfamily Elateroidea.
Worldwide and British representation. About 9300 species worldwide; genera at least 900. 65 species in Britain; genera in Britain 26; Elater, Megapenthes, etc. E.g., Elater sanguinolentus; Megapenthes lugens.
General comments. The adult prothorax (the first segment of the thorax) and the mesothorax (the second segment) are freely movable on one another, and the underside of the former bears a pointed, rearward prosternal extension which engages and disengages with a cavity in the under-side of the latter. This arrangement constitutes the familiar ‘clicking mechanism’, whereby the beetle clicks and jumps to right itself or as a means of escape. The labrum protrudes forwards of the front of the head, and unlike the situation in Eucnemidae it is visible from above..
Illustrations. • Ampedus sanguinolentus (Rye & Fowler IX1). • Megapenthes lugens: B. Ent. 694. • Megapenthes lugens: B. Ent. 694, legend+text. • Megapenthes lugens: B. Ent. 694, text cont.. • Megapenthes lugens(Janson 184). • Agriotes, Athous and Corymbites: Curtis (1860, Plate F). • Agriotes, Athous and Corymbites: Curtis (1860, legend). • Agriotes, Athous and Corymbites: Curtis (1860, legend cont.). • Assorted Click-beetles: Curtis (1860, Plate G). • Agrypnus, Cardiophorus, Cryptohypnus, Elater (3 spp.), Fleutiauxellus, Hypnoidus, Negastrius, Zorochros (with Dirhagus): Fowler 4, 105 (1890). • Fowler 4, 105 (1890): original legend.. • Elater (6 spp.), Ischnodes, Megapenthes, Melanotus (3 spp.), Procraerus: Fowler 4, 106 (1890). • Fowler 4, 106 (1890): original legend.. • Adrastus, Athous (7 spp.), Cidnopus (2 spp.), Sericus, Synaptus: Fowler 4, 107 (1890). • Fowler 4, 107 (1890): original legend.. • Adrastus, Agriotes (4 spp.), Anostirus, Ctenicera, Dalopius, Selatosomus: Fowler 4, 108 (1890). • Fowler 4, 108 (1890): original legend.. • Denticollis (2 spp.), Prosternon, Selatosomus (5 spp, with Dascillidae and Scirtidae): Fowler 4, 109 (1890). • Fowler 4, 109 (1890): original legend.. • Athous, Cardiophorus and Negastrius, with unrelated taxa: Fowler Suppl. 15, 1913. • Fowler Suppl. 15, 1913: original legend.
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. British insects: the families of Coleoptera. Version: 2nd January 2012. http://delta-intkey.com’.
