British insects: the families of Coleoptera
Adults. Beetles terrestrial (sometimes found in ants nests); when inundated, walking in water or free-swimming by conventional ambulatory motion of the legs, not diving strongly; moving in the water by alternate, walking leg movements. Beetles 2.5–4 mm long; body length/maximum body width 1–2.62. Beetles oval to elongate-oval; dorsally somewhat convex to dorsally strongly convex; not necked; somewhat waisted; yellow-brown. Beetles entirely unicolorous yellow. Upper surfaces of body not bristly; with neither scales nor scale-like setae. Inclination of the head slight.
Eyes two; strongly protuberant, or not strongly protuberant; without bristles. Mandibles present, or absent or vestigial (?); if present, with a well developed mola, or with a reduced mola, or without a mola. The mandibular apices simple. The incisor edges of the mandibles simple, or with a single tooth, or with two or more teeth. The maxillae with distinct galea and lacinia apically to the palp. The maxillary palps not especially elongated. The apical segment of the maxillary palps cylindrical to fusiform. The apical segment of the labial palps not expanded apically. Antennae short, or about half the insect's head to tail length; not strongly asymmetric; 11 segmented. Antennal scape swollen. Antennae filiform. Antennal insertions visible from above.
Prothorax without notopleural sutures. Mid-and hind-legs not as in Gyrinidae (q.v.). The fore-leg coxal cavities broadly open; narrowly separated; strongly transverse; without lateral extensions; internally open. Hind coxae not extended laterally to meet the elytra; posteriorly shaped to receive the retracted femur. The hind coxae not produced behind into flat plates partly concealing the hind femora. Hind coxae without the steep transverse declivity characteristic of Dryopoidea. The inner parts (processes) of the hind coxae not incorporated with the metasternum in a flat, median longitudinal keel. The hind femora not especially enlarged. Tarsal segmentation formula 5, 5, 5. Some of the tarsi exhibiting conspicuously bilobed segments (segment 4 only). None of the tarsi with hidden segments. The 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; without an associated empodium. Hind tarsi with at least as many segments as the mid-tarsi; 5-segmented.
Elytra exposing no more than part of the terminal tergite; soft (and hairy). Scutellary striole absent. Wings well developed. Exposed abdominal sternites 5. Abdominal segment 8 apparently without functional spiracles.
Adults in damp places. Sub-aquatic or terrestrial?.
Larvae. The larvae campodeiform; elongate and more or less parallel-sided; vestiture restricted to fine hairs or setae; dorsally heavily pigmented or sclerotized; more or less heavily pigmented. The antennae 5–10 segmented (five or more); more than 0.5 x the width of the head. Stemmata fewer than 6. Frontoclypeal suture between frons and clypeus indistinct or absent. The labrum and head capsule separated by a complete suture. Apices of the mandibles with a single lobe or tooth. The maxillary palps 4 segmented. The labium without ligula between the palps. The labial palps 4 segmented. The mesothoracic legs 5 segmented (including the pretarsus); with 1 movable claw. Visible abdominal segments 8, or 9 (?). Tergum 9 of the abdomen entirely dorsal.
The larvae aquatic. The abdomen exhibiting functional abdominal spiracles; with functional spiracles confined to the the eighth segment. The larvae with anal gill tufts. The abdominal apex with a respiratory chamber, formed from the 8th and 9th terga and enclosing a pair of enlarged spiracles. Abdominal tergum 8 without amature. The larvae phytophagous (on water plants).
The campodeiform larvae with anal gills and long, multi-segmented antennae.
Worldwide and British representation. 1 species in Britain (P. serricornis). Recorded from Scotland, Northern England, South-west England and Wales, South-eastern England, and Ireland.
Classification. Suborder Polyphaga; Infraorder Elateriformia; Superfamily Eucinetoidea; Scirtidae.
General comments on this taxon. Beetles with yellow legs.
Miscellaneous. • Microcara, Cyphon, Prionocyphon, Hydrocyphon, Scirtes (with Psephenidae and Lycidae): Fowler 4, 110 (1890).
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: water beetles. Version: 18th September 2012. http://delta-intkey.com’.