Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


Including Psoidae, excluding Lyctidae.

Wood-borers, Augur beetles.

General appearance. 2.5–9 mm long. Body length/maximum body width 2.33–3.72. Elytral length/pronotal length 1.8–3.9. 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 elongate; cylindric; not necked; conspicuously waisted; black or brown. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae.

Detailed morphology. The head covered by the thorax. Eyes strongly protuberant; without bristles; finely facetted. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a well developed mola (Dinoderinae), or with a reduced mola to without a mola; with reduced prosthecae, or without prosthecae. The mandibular apices simple. The incisor edges of the mandibles simple, or with a single tooth (some Bostrichinae). 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; not elbowed; 8–11 segmented. Antennal scape not swollen. Antennae clubbed. Antennal clubs 2 segmented, or 4 segmented (loose). Antennal insertions hidden from above.

Cervical sclerites absent. Pronotal length/maximum pronotal width 0.68–1.35. The pronotum with lateral keels (pronotal carinae), or without lateral keels; keels when present, incomplete. Prothorax hooded and concealing the head, its front covered with large bumps. Prothorax without notopleural sutures. Scutellum conspicuous; elevated above the mesoscutum in lateral view, or not elevated; anteriorly simple; posteriorly broadly rounded or obtusely angulate, or truncate. The prosternal process present, or absent (in some Bostrichinae); if present incomplete; when present, falling short of the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally; broadly open to narrowly open; medianly confluent; slightly transverse, or circular to longer than wide; without lateral extensions; internally closed by a slender bar, or broadly closed internally. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by less than the shortest diameter of the cavity. The mid-leg coxal cavities contiguous (Dinoderinae), or narrowly separated (Bostrichinae); not or scarcely oblique; open laterally, or closed laterally. Hind-leg coxae contiguous or narrowly separated; extending laterally to meet the elytra, or not markedly extended laterally; not shaped posteriorly to receive the femur. Tarsal segmentation formula 5, 5, 5. The tarsi without bilobed segments; of British species, 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. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 1.5–2.85. Elytra exposing no more than part of the terminal tergite; hard (strongly sclerotized); often spiny (distally). Elytra with six or more longitudinal lines of punctures, 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 present (Dinoderinae), or absent (Bostrychinae). Wings well developed. Wings with an anal lobe, or without an anal lobe. Wings without a medial fleck. Abdominal sternites 5 (the first hardly longer than the second or the third); all articulated and moveable. Abdominal segment 8 with apparently functional spiracles. The male external genitalia bostrichoid.

Adult habitat, ecology. Not predacious; on living vegetation, or in rotting wood, or in dried plant material, or in stored plant products; variously phytophagous, or consuming decaying plant material, or eating dried plant material or stored plant products, or boring into living wood, or consuming rotting wood, or boring into dead wood (with many boring into tree trunks, branches and twigs of dead or dying trees, others into sapwood).

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae elongate and more or less parallel-sided, or oblong to ovate; C-shaped in lateral view. Body circular in cross-section, or somewhat flattened, or circular in cross-section to somewhat flattened. Vestiture restricted to fine hairs or setae. The larvae dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present, or absent; on either side of the larval head when present, 1 (Euderiinae, some Psoinae). 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, or bilobed or bidentate (Euderiinae, some Psoinae), or trilobed or tridentate (Dinoderinae). The maxillary palps 2 segmented, or 3 segmented. The labium without ligula between the palps (Dinoderinae), or with a short ligula between the palps. Labial palps present and segmented; 1 segmented (Dinoderinae), or 2 segmented. Mesothoracic legs present and segmented; 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 ot annular-uniforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.

Larvae often tunnelling in moribund and newly fallen timber. Dinoderus larvae commonly feed in stems of bamboos and other monocots, and can be pests in cane furniture and basket-work, while some Lyctinae reduce dried wood to fine powder (‘powderpost beetles’); boring into living wood and boring into dead wood.

Classification. Suborder Polyphaga; Infraorder Bostrichiformia; Superfamily Bostrichoidea.

Representation in Britain and Ireland, and worldwide. About 700 species worldwide. 3 species in Britain; genera in Britain 3; Bostrichus, Rhyzopertha, Stephanopachys. E.g., Bostrichus capucinus (Capuchin Beetle: extinct?).

General comments. Cervical sclerites absent; the tarsi more variable in non-British species.

Illustrations. • Bostrichus capucinus (Capuchin beetle): B. Ent. 271. • Bostrichus capucinus: B. Ent. 271, legend+text. • Bostrichus capucinus: B. Ent. 271, text cont.. • Bostrichus capucinus and Rhizopertha pusilla (= ?, with Cisidae, etc.): Fowler 4, 119 (1890). • Fowler 4, 119 (1890): original legend.. • Stephanopachys substriatus (with Anobiidae): Fowler 4, 118 (1890). • Fowler 4, 118 (1890): original legend. • Dinoderus minutus (Bamboo borer, with unrelated taxa). • Fowler Suppl. 16, 1913: original legend..

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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.’.