British insects: the families of Coleoptera
British insects: the families of Coleoptera |
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Including Epimetopidae, Georissidae, Georyssidae, Helophoridae, Hydrochidae, Spercheidae, Sphaeridiidae.
Water-, Pond-, Marsh-beetles, Scavenger Water-beetles.
General appearance. 1.5–38 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. The maxillary palps conspicuously elongated, sometimes longer than the antennae (apparently having taken over their sensory functions). Antennae very short (and modified for involvement in respiration); 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. Tarsal segmentation formula 5, 5, 5. The tarsi without bilobed segments; with a tiny basal segment that is hard to detect, or without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi, or with one segment fewer than the mid-tarsi; 4-segmented, or 5-segmented. Mid-leg tarsi 4-segmented, or 5-segmented; pentamerous, or tetramerous. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple, or one-toothed or bifid; with an empodium between them (this setose, sometimes with more than three setae). Hind tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented; modified for swimming, or not modified for swimming. Elytral length/maximum width across the elytra 0.93–1.95. Elytra exposing no more than part of the terminal tergite; smooth. Scutellary striole present, or absent. Wings well developed, or absent or much reduced. Exposed abdominal sternites 4–6; all articulated and movable, or comprising both fused and movable components; immovably joined when present, 2. Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles.
Adult habitat, ecology. Water-beetles (storing air under the elytra, into which the spiracles open, when underwater), or land-dwellers (British representation of the former including the Giant Water-beetle, Hydrophilus piceus); when aquatic, 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.
Larvae. Larvae aquatic, or non-aquatic; usually predacious; when non-aquatic, in decaying plant material, or in dung.
Classification. Suborder Polyphaga; Infraorder Staphyliniformia; Superfamily Hydrophiloidea.
Worldwide and British representation. About 2800 species worldwide; genera about 160. 89 species in Britain; genera in Britain 20; Berosus, Helophorus, Hydrobius, Hydrochus, Hydrochara, Hydrophilus, Spercheus, Sphaeridium, etc. 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).
General comments. Drab beetles, with maxillary palps longer than the antennae. Some stridulate when alarmed.
Illustrations. • Berosus signaticollis (Berosus Water-beetle: B. Ent. 240). • Berosus signaticollis: B. Ent. 240, legend+text. • Berosus signaticollis: B. Ent. 240, text cont.. • Georyssus crenulatus, with Dryopidae, Elmidae and Heteroceridae: Fowler 3, 98 (1889). • Fowler 3, 98 (1889): original legend.. • Helophorus rufipes (Broad Elophorus: B. Ent. 466). • Helophorus rufipes: B. Ent. 466, legend+text. • Helophorus rufipes: B. Ent. 466, text cont.. • Hydrobius fuscipes (Salt-water Hydrobius: B. Ent. 243). • Hydrobius fuscipes: B. Ent. 243, legend+text. • Hydrobius fuscipes: B. Ent. 243, text cont.. • Hydrochus elongatus (Elongated Hydrochus: B. Ent. 359). • Hydrochus elongatus: B. Ent. 359, legend+text. • Hydrochus elongatus: B. Ent. 359, text cont.. • Hydrochara carabiodes (Globose Pond-beetle: B. Ent. 159). • Hydrochara caraboides (details, B. Ent. 159). • Hydrochara caraboides: B. Ent. 159, legend+text. • Hydrochara caraboides: B. Ent. 159, text cont.. • 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). • Spercheus emarginatus: B. Ent. 394, legend+text. • Spercheus emarginatus: B. Ent. 394, legend+text. • Sphaeridium scarabaeoides (B. Ent. 518). • Sphaeridium scarabaeoides: B. Ent. 518, legend+text. • Sphaeridium scarabaeoides: B. Ent. 518, text cont.. • Laccobius sinuatus, L. striatulus and Paracymus aenus: Fowler Suppl. 2, 1913. • Fowler Suppl. 2, 1913: original legend. • Cercyon, Helophorus, Hydrochus, Laccobius and Sphaeridium (with Hydraenidae and Staphylinidae): Fowler Suppl. 3, 1913. • Fowler Suppl. 3, 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’.
