British insects: the families of Coleoptera
British insects: the families of Coleoptera | |
Crawling Water-beeetles.
General appearance. 2–4.5 mm long. Body length/maximum body width 1.45–2.5. Elytral length/pronotal length 3.24–4.05. Base of prothorax not or scarcely 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; conspicuously necked to not necked; not waisted to somewhat waisted; yellowish. 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. Eyes not strongly protuberant; without bristles; coarsely facetted. The maxillae with an outer palpiform lobe (the galea) additional to the 4-segmented maxillary palp. Antennae very short to short; 11 segmented; filiform. Antennal insertions visible from above; not in fossae. Mandibular prosthecae well developed, or absent. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.43–0.66. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax with notopleural sutures. Metaventrite with a transverse groove, or without a transverse groove. Hind coxae immovably fixed to the metasternum and dividing the first abdominal sternite; much expanded and extended laterally to meet the elytra; produced behind into flat plates which conceal the hind femora when retracted (and also concealing the basal abdominal sternites). Tarsal segmentation formula 5, 5, 5. The tarsi without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented (and modified for swimming, cf. the hind pair); pentamerous. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple. Hind tarsi with as many segments as the mid-tarsi; 5-segmented (modified for swimming); modified for swimming (via long hairs). Elytral length/maximum width across the elytra 1.15–1.52. Elytra exposing no more than part of the terminal tergite; darkly, conspicuously striate. 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, or 3. Abdominal segment 8 with apparently functional spiracles.
Adult habitat, ecology. Water-beetles; not predacious; phytophagous (mainly on green algae).
Larvae. Larvae aquatic; predacious (with short, curved, hollow suctorial mandibles). The larvae with 4-segmented antennae, legs with single claws, and an elongate 10th segment with cerci.
Classification. Suborder Adephaga; Superfamily Caraboidea.
Worldwide and British representation. About 200 species worldwide; genera 5. 18 species in Britain; genera in Britain 3; Brychius, Haliplus, Peltodytes. E.g., Haliplus obliquus.
General comments. Boat-shaped beetles, the scutellum not visible; crawling under water, and swimming, via alternate leg movements.
Illustrations. • Haliplus fulvus: B. Ent. 730. • Haliplus fulvus: B. Ent. 730, legend+text. • Haliplus fulvus: B. Ent. 730, text cont.. • Haliplus fulvus (Janson 43). • Haliplus obliquus (Rye & Fowler III4).
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’.
