British insects: the families of Coleoptera
British insects: the families of Coleoptera | |
= Elmididae, Elminthidae, Helmidae, Helminthidae, Limniidae.
Riffle Beetles, Water-beetles.
General appearance. 1.8–4 mm long. Body length/maximum body width 1.8–3.1. Elytral length/pronotal length 1.8–4.7. 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 oval to elongate-oval; without ventral body cavities for reception of the legs; not necked; somewhat waisted; conspicuously long-legged. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.
Detailed morphology. Inclination of the head slight to strong. Eyes not strongly protuberant; without bristles. Antennae short; 7–11 segmented. Antennal scape not swollen. Antennae filiform. Antennal insertions visible from above; not in fossae. Pronotal length/maximum pronotal width 0.6–1.1. Prothorax without notopleural sutures. The scutellum elevated. Metaventrite with a transverse groove. Hind coxae posteriorly shaped to receive the retracted femur; with a steep transverse declivity against which the femur retracts. Tarsal segmentation formula 5, 5, 5. The tarsi 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. The claws of the mid-leg tarsi simple, or one-toothed or bifid. Hind tarsi with as many segments as the mid-tarsi; 5-segmented. Elytral length/maximum width across the elytra 1.3–2.5. Elytra exposing no more than part of the terminal tergite; not truncate. Scutellary striole present, or absent. Wings well developed, or absent or much reduced. Exposed abdominal sternites 5–6; comprising both fused and movable components; immovably joined 3. Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles.
Adult habitat, ecology. Water-beetles (in running water); moving in the water by alternate, walking leg movements; not predacious; phytophagous; in living vegetation.
Larvae. Larvae aquatic; not predacious; phytophagous; on living vegetation.
Classification. Suborder Polyphaga; Infraorder Elateriformia; Superfamily Dryopoidea.
Worldwide and British representation. Genera about 30 (?). 11 species in Britain; genera in Britain 8; Elmis, Esolus, Limnius, Macronychus, Normandia, Oulimnius, Riolus, Stenelmis. E.g., Limnius volkmari (Volckmar's Elmis Water-beetle).
Illustrations. • Limnius volckmari (Volckmar's Water-beetle: bent294). • Limnius volckmari (details, B. Ent. 294). • Limnius volckmari: B. Ent. 294, legend+text. • Elmis aenea, Esolus, Limnius, Macronychus, Oulimnius (with Dryopidae, Heteroceridae and Hydrophilidae): Fowler 3, 98 (1889). • Fowler 3, 98 (1889): 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’.
