Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz




General appearance. 2–5 mm long. Body length/maximum body width 1.45–3.1. Elytral length/pronotal length 1.85–3.7. 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 to elongate-oval; conspicuously necked to not necked; not waisted; usually mottled. Upper surfaces of body 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; deeply accommodating the antennae in an anterior notch; without bristles. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a well developed mola. The mandibular apices simple. The incisor edges of the mandibles simple. 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 not swollen. Antennae filiform, or serrate. Antennal insertions visible from above.

Cervical sclerites absent. Pronotal length/maximum pronotal width 0.55–0.95. The pronotum with lateral keels (pronotal carinae), or without lateral keels; keels when present, complete, or incomplete. Prothorax without notopleural sutures. Scutellum conspicuous, or highly reduced; elevated above the mesoscutum in lateral view, or not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or truncate, or emarginate. The prosternal process complete, or incomplete; falling short of the mesoventrite to slightly overlapping the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally, or closed behind externally; narrowly open, or narrowly closed, or broadly closed; medianly confluent, or narrowly separated; strongly transverse to slightly transverse; with narrow lateral extensions, or without lateral extensions; broadly closed internally. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by less than the shortest diameter of the cavity, or more than the shortest diameter of the cavity. The mid-leg coxal cavities narrowly separated, or moderately to widely separated; not or scarcely oblique, or markedly oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; much enlarged; not markedly extended laterally; not shaped posteriorly to receive the femur. Tarsal segmentation formula 4, 4, 4. The tarsi exhibiting bilobed segments; with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth. Front tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented (depending on interpretation). Mid-leg tarsi 4-segmented, or 5-segmented; pseudotetramerous; the penultimate segment distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi one-toothed or bifid; without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented (the basal segment longer than the rest together).

Elytral length/maximum width across the elytra 0.9–1.9. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite to at least three complete abdominal tergites; truncate; non-glabrous (clothed with recumbent hairs). Elytra with six or more impressed striae, or apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae; the lines per elytron when more than five, 10. Scutellary striole absent. Wings well developed. Wings with an anal lobe, or without an anal lobe. Abdominal sternites 5; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles. The male external genitalia chrysomeloid.

Adult habitat, ecology. On living vegetation; phytophagous (especially associated with legumes).

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae scarabaeiform; elongate and more or less parallel-sided; C-shaped in lateral view. Body circular in cross-section. Vestiture restricted to fine hairs or setae. The larvae dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 2 segmented, or 3 segmented; 0.15–0.5 x the head width. 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 distinct. The labrum and head capsule separated by a complete suture. Apices of the mandibles with a single lobe or tooth. The maxillary palps 1–3 segmented. Labial palps absent or non-segmented. Mesothoracic legs present and segmented to much reduced or absent; 0 segmented, or 3–5 segmented; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen entirely dorsal. The abdomen having functional spiracles on anterior segments (these annular, annular-uniforous or annular-biforous); without spiracular tubes. The larvae without abdominal gills. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The posterior segments without swimming hairs. The last abdominal segment without cerci.

Larvae often in dried plant material and in stored plant products; phytophagous and eating dried plant material or stored plant products (seed feeders, especially on legumes, but also Compositae, Malvaceae, Convolvulaceae, etc.).

Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Chrysomeloidea.

Representation in Britain and Ireland, and worldwide. About 1300 species worldwide; genera about 60. 13 species in Britain; genera in Britain 5; Acanthoscelides, Bruchidius, Bruchus, Callosobruchus, Zabrotes.

General comments. Small, ovoid, compact beetles with the head deflexed and a long neck; body with recumbent hairs, often spotted.

Illustrations. • Bruchidius ater: B. Ent. 754. • Bruchidius ater: B. Ent. 754, legend+text. • Bruchidius ater: B. Ent. 754, text cont.. • Donacia (11 spp.), Orsodacne (2 spp.): Fowler 4, 126 (1890). • Fowler 4, 126 (1890): original legend.. • Bruchidius (3 spp.), Bruchus (5 spp.), Callosobruchus (with Cerambycidae): Fowler 4, 125 (1890). • Fowler 4, 125 (1890): original legend. • Bruchus rufimanus and Callosobruchus chinensis, with Cerambycidae and Chrysomelidae Fowler Suppl. 1. • Fowler Suppl. 17, 1913: original legend. • Bruchidius ater (Janson 227). • Bruchus, Bruchidius.

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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.’.