British insects: the families of Coleoptera
British insects: the families of Coleoptera | |
= Dytiscidae part; including Phreatodytidae.
Burrowing Water-beetles.
General appearance. 4–4.5 mm long. Body length/maximum body width 1.38–2.1. Elytral length/pronotal length 2.05–3.75. 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 not necked; yellowish- or reddish-brown. 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; finely facetted. The maxillae with an outer palpiform lobe (the galea) additional to the 4-segmented maxillary palp. Antennae short; 11 segmented; filiform. Antennal insertions hidden from above; not in fossae. Mandibular prosthecae present but reduced, or absent. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.4–0.65. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax with notopleural sutures. Metaventrite 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 (with characteristic, conspicuous inner longitudinal plates covering the articulations of the trochanters). The inner parts of the hind coxae constituting longitudinal plates that are fused to one another and joined with the metasternum, endowing the beetle ventrally with a flat, median longitudinal keel. 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. Hind tarsi with as many segments as the mid-tarsi; 5-segmented; modified for swimming, or not modified for swimming. Elytral length/maximum width across the elytra 0.92–1.56. Elytra exposing no more than part of the terminal tergite; glossy. Scutellary striole 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; diving and ‘Rowing’ by parallel-simultaneous leg movements; predacious, or not predacious (?).
Larvae. Larvae aquatic; probably predacious (but not digesting extra-orally).
Classification. Suborder Adephaga; Superfamily Caraboidea.
Worldwide and British representation. About 230 species worldwide; genera 12 (especially tropical). 2 species in Britain; genera in Britain 1; Noterus. E.g., N. clavicornis (Marsham's Noterus Water-beetle).
General comments. Beetles dorsally very convex and boat-shaped, the scutellum invisible; burrowing in ponds and marshes..
Illustrations. • Noterus clavicornis (Marsham's Water-beetle: B. Ent. 236). • Noterus clavicornis (details, B. Ent. 236). • Noterus clavicornis: B. Ent. 236, legend+text. • Noterus clavicornis: B. Ent. 236, text cont..
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’.
