Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


Including Dorcatominae, Ectrephidae, Gnostidae.

Death-watch Beetles, Woodworms.

General appearance. 1.3–7 mm long. Body length/maximum body width 1.35–3.63. Elytral length/pronotal length 1.4–4.7. 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-oval to elongate; dorsally somewhat convex; not necked; not waisted to somewhat waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; exhibiting stiff, erect, dark bristles, or not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae. Beetles not clicking and ‘jumping’.

Detailed morphology. Beetles not prognathous. The head covered by the thorax. Inclination of the head strong. Eyes strongly protuberant, or not strongly protuberant; without bristles; finely facetted. Ocelli absent. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles without a mola; without prosthecae. The mandibular apices simple. The incisor edges of the mandibles simple, or with a single tooth. The maxillae with distinct galea and lacinia apically to the palp. The apical segment of the maxillary palps cylindrical to fusiform, or somewhat expanded and truncate to subtriangular, or securiform to cultriform. The apical segment of the labial palps more or less expanded apically, or not expanded apically. Antennae very short to long, but not exceeding the insect’s head to tail length; (2–)9–11 segmented. Antennal scape not swollen. Antennae filiform, or clubbed, or serrate, or pectinate. Antennal clubs if present, 3 segmented. Antennal insertions visible from above, or hidden from above; ‘countersunk’ within saucer-like fossae.

Cervical sclerites absent. Pronotal length/maximum pronotal width 0.32–1.5. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax without notopleural sutures. Scutellum conspicuous to absent; when applicable, elevated above the mesoscutum in lateral view; anteriorly when present, simple; posteriorly narrowly rounded or acute to broadly rounded or obtusely angulate. The prosternal process variously complete, or incomplete; falling short of the mesoventrite to moderately or strongly overlapping 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; medianly confluent, or narrowly separated to quite widely separated; slightly transverse, or circular to longer than wide; without lateral extensions; internally closed by a slender bar. 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; closed laterally. Hind-leg coxae contiguous or narrowly separated; extending laterally to meet the elytra, or not markedly extended laterally; posteriorly shaped to receive the retracted femur (with a transverse cavity). 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 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 to one-toothed or bifid; without an associated empodium. Hind tarsi with as many segments as the mid-tarsi, or with one segment fewer than the mid-tarsi; 5-segmented (rarely 4?).

Elytral length/maximum width across the elytra 0.98–2.65. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite; hard. Elytra with six or more longitudinal lines of punctures, or 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 present, or absent. Wings well developed, or absent or much reduced; fringed with long hairs on the hind margin, or not fringed. Wings with an anal lobe (mostly), or without an anal lobe (Eucradinae). Wings without a medial fleck. Abdominal sternites 5; comprising both fused and moveable components, or all fused and immoveable. Basal abdominal sternites immovably joined 2 (Xyletininae), or 3, or 5–6 (e.g., Dorcatominae). Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles. The male external genitalia bostrichoid.

Adult habitat, ecology. In decaying plant material, or in dried plant material, or under bark, or in stored plant products (etc.); variously feeding on dried animal remains, 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, or coprophagous (but mostly wood borers, including pests of structural timbers and furniture).

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 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 1 segmented, or 2 segmented. Stemmata present, or absent; on either side of the larval head when present, 1. 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 to trilobed or tridentate. The maxillary palps 2–4 segmented. The labium without ligula between the palps, or with a short ligula between the palps. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented, or much reduced or absent; 0 segmented (Dorcatoma), or 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; without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.

Larvae in rotting wood, under bark, associated with fungi, and in stored plant products (notoriously boring in dead wood); eating dried plant material or stored plant products and boring into dead wood, or mycetophagous (Dorcatominae fruit bodies of bracket fungi and puff balls).

Larvae C-shaped with well developed legs, soft, head hypognathous with very small 3-segmented antennae, abdomen 10 segmented with the last one very small.

Classification. Suborder Polyphaga; Infraorder Bostrichiformia; Superfamily Bostrichoidea.

Representation in Britain and Ireland, and worldwide. About 50 species in Britain; genera in Britain about 25; Anobium, Ptinomorphus, Xyletinus, etc. E.g., Ptinomorphus imperialis; Xyletinus longitarsis (Serrated-horned Ptinus).

General comments. Small subcylindric or ovoid, reddish or dark brown beetles, with antennal insertions separated by more than the length of the scape; the hind coxae with a transverse concavity for reception of the femur..

Illustrations. • Anobium pertinax Linn. (Obstinate Death-watch beetle; cf. A. punctatum): B. Ent. 387. • Anobium pertinax (B. Ent. 387, legend+text. • Anobium pertinax (B. Ent. 387, text cont.. • Xyletinus longitarsis (Serrate-horned Ptinus: B. Ent. 375). • Xyletinus longitarsis (details, B. Ent. 375). • Xyletinus longitarsis: B. Ent. 375, legend+text. • Xyletinus longitarsis: B. Ent. 375, text cont.. • Anobium, Dryophilus, Grynobius, Hadrobregmus, Ptonomorphus (with Ptinidae): Fowler 4, 117 (1890). • Fowler 4, 117 (1890): original legend.. • Anitys, Coenocara, Dorcatoma, Ernobius, Lasioderma, Ochina, Ptilinus, Xestobium (with Stephanopachys): Fowler 4, 118 (1890). • Fowler 4, 118 (1890): original legend. • Ernobius abietis, with Cerambycidae etc.: Fowler Suppl. 16, 1913. • Fowler Suppl. 16, 1913: original legend. • Ptinomorphus imperialis (Rye & Fowler X1).

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.’.