British Insects: the Families of Coleoptera
British Insects: the Families of Coleoptera |
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Including Epimetopidae, Georissidae, Georyssidae, Helophoridae, Hydrochidae, Spercheidae.
Water-, Pond-, Marsh-beetles.
General appearance. 1.5–37 mm long. Body length/maximum body width 1.3–2.55. Elytral length/pronotal length 1.7–4.85. 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; not necked; somewhat 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. Eyes not strongly protuberant; without bristles. Antennae very short; not strongly asymmetric; not elbowed; 7–9 segmented; clubbed (the club hairy). Antennal clubs preceded by a cupule, or without a cupule. Antennal insertions visible from above, or hidden from above. Mandibular prosthecae well developed.
Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.25–1.08. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Metaventrite with a transverse groove, or without a transverse groove. The tarsi without bilobed segments; with a tiny basal segment that is hard to detect, or without ‘hidden’ segments. Mid-leg tarsi 4-segmented, or 5-segmented; pentamerous, or tetramerous. Claws of the mid-leg tarsi not appendaged. Front tarsi with as many segments as the mid-tarsi, or with one segment fewer than the mid-tarsi; 4-segmented, or 5-segmented. Hind tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented; modified for swimming, or not modified for swimming. Tarsal claws simple, or one-toothed or bifid; with an empodium between them (this setose, sometimes with more than three setae). Elytral length/maximum width across the elytra 0.93–1.95. Elytra covering most of the abdomen; exposing no more than part of the terminal tergite; smooth. Scutellary striole present, or absent. Wings well developed, or absent or much reduced.
Visible abdominal sternites 4–6; immovably joined 0, or 2. Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles.
Habitat, ecology. Water-beetles, or land-dwellers; moving in the water by alternate, walking leg movements; not predacious; phytophagous, or consuming decaying plant material, or coprophagous; when non-aquatic, in decaying plant material, or associated with dung.
General comments. Drab beetles, with maxillary palps longer than the antennae. Some stridulate when alarmed.
Larvae. Larvae aquatic, or non-aquatic; usually predacious; when non-aquatic, in decaying plant material, or in dung.
Classification. Suborder Polyphaga; Superfamily Hydrophiloidea.
British representation. Genera 20; 89 species. E.g., Berosus signaticollis (Berosus Water-beetle); Helophorus rufipes (Broad Elophorus); Hydrobius fuscipes (Salt-water Hydrobius); Hydrochus elongatus (Elongated Hydrochus); Hydrochara caraboides (Globose Pond-beetle); Hydrophilus piceus (Great Water-beetle); Spercheus emarginatus (Notch-headed Hydrophilus); Sphaeridium scarabaeoides (4-spotted Dung-beetle).
Illustrations. • Berosus signaticollis (Berosus Water-beetle: B. Ent. 240). • Berosus signaticollis (B. Ent. 240, legend+text). • Helophorus rufipes (Broad Elophorus: B. Ent. 466). • Hydrobius fuscipes (Salt-water Hydrobius: B. Ent. 243). • Hydrochus elongatus (Elongated Hydrochus: B. Ent. 359). • Hydrochara carabiodes (Globose Pond-beetle: B. Ent. 159). • Hydrochara caraboides (details, B. Ent. 159). • Hydrochara caraboides: B. Ent. 159, legend+text. • Hydrophilus piceus (Great Water-beetle: B. Ent. 239). • Hydrophilus piceus (B. Ent. 239, legend+text). • Hydrophilus piceus (B. Ent. 239, text cont.). • Spercheus emarginatus (Notch-headed Hydrophilus: B. Ent. 394). • Sphaeridium scarabaeoides (B. Ent. 518).
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: 9th June 2008. http://delta-intkey.com’.
