Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


Including Cyphonidae, Elodidae, Helodidae.

Water-nymph beetles, Marsh beetles.

General appearance. 1.5–5.5 mm long. Body length/maximum body width 1–2.62. Elytral length/pronotal length 3.14–8.2. 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; dorsally somewhat convex to dorsally strongly convex; not necked; somewhat waisted; yellow-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 strongly protuberant, or not strongly protuberant; without bristles. The labrum at least partly visible in antero-dorsal view, or concealed beneath the clypeus; labrum where recorded, mostly moderately to heavily sclerotized. Mandibles present, or absent or vestigial; with a well developed mola, or with a reduced mola, or without a mola. The mandibular apices when mandibulate, 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 apical segment of the maxillary palps cylindrical to fusiform. The apical segment of the labial palps not expanded apically. Antennae short to about half the insect's head to tail length; 11 segmented. Antennal scape swollen. Antennae filiform (flattened). Antennal insertions visible from above; ‘countersunk’ within saucer-like fossae, or not in fossae.

Cervical sclerites present. Pronotal length/maximum pronotal width 0.22–0.83. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax without notopleural sutures. Scutellum conspicuous; elevated above the mesoscutum in lateral view, or not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate. The prosternal process complete; slightly overlapping the mesoventrite, or moderately or strongly overlapping the mesoventrite. Metaventrite with a transverse groove, or without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally; broadly open; narrowly separated; strongly transverse; without lateral extensions; internally open. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by less than the shortest diameter of the cavity. The mid-leg coxal cavities contiguous, or narrowly separated; not or scarcely oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; extending laterally to meet the elytra; posteriorly shaped to receive the retracted femur (transversely excavated). Tarsal segmentation formula 5, 5, 5. The tarsi exhibiting bilobed segments (segment 4 only); without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous; the penultimate segment not distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple; without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 0.85–2.1. Elytra exposing no more than part of the terminal tergite; soft. Elytra apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae. Scutellary striole absent. Wings well developed. Wings with an anal lobe. Wings without a medial fleck. Abdominal sternites 5; all articulated and moveable, or comprising both fused and moveable components. Basal abdominal sternites immovably joined 2, or 3. Abdominal segment 8 apparently without functional spiracles. The male external genitalia not classified.

Adult habitat, ecology. The adults seemingly all land-dwellers (but associated with helophytic plants). Beetles but often found floating or struggling in water. Often on the surfaces of vegetation in damp places.

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae campodeiform; elongate and more or less parallel-sided. Body somewhat flattened. Vestiture restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized; ventrally more or less heavily pigmented. The antennae 5–20 segmented (? - “five or more”); more than 0.5 x the width of the head. Stemmata present; on either side of the larval head 1–3. The larval fronto-clypeus not extended forwardly. The 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. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented; 5 segmented; with 1 moveable claw. Visible abdominal segments 8, or 9. Tergum 9 of the abdomen entirely dorsal. The abdomen with functional spiracles confined to the the eighth segment (these enlarged); without spiracular tubes. The larvae with abdominal gills; 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 last abdominal segment without cerci.

Larvae aquatic; usually in stagnant water, in ponds, bogs, marshes, tree holes, etc.; detritus feeders, with specialized filter-feeding adaptations for concentrating suspended small prticles of organic matter.

The campodeiform larvae with anal gills; unique among those of Endopterygotes in having long, multi-segmented antennae.

Classification. Suborder Polyphaga; Infraorder Elateriformia; Superfamily Eucinetoidea.

Representation in Britain and Ireland, and worldwide. About 1400 species worldwide; genera about 50. 16 species in Britain; genera in Britain 6; Cyphon, Elodes, Hydrocyphon, Microcara, Prionocyphon, Scirtes. E.g., Hydrocyphon deflexicollis.

General comments. The adults are adept at jumping, using their enlarged hind legs.

Illustrations. • Hydrocyphon deflexicollis: B. Ent. 602. • Hydrocyphon deflexicollis: B. Ent. 602, legend+text. • Hydrocyphon deflexicollis: B. Ent. 602, text cont.. • Microcara, Cyphon, Prionocyphon, Hydrocyphon, Scirtes (with Psephenidae and Lycidae): Fowler 4, 110 (1890). • Fowler 4, 110 (1890): original legend.. • Elodes marginata and E. minuta (with Elateridae and Dascillidae): Fowler 4, 109 (1890). • Fowler 4, 109 (1890): original legend.. • Hydrocyphon deflexicollis (Janson 188).

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. Insects of Britain and Ireland: the families of Coleoptera. Version: 16th May 2016.’.