Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz



Pinhole Bark-borers.

General appearance. 5–8 mm long. Body length/maximum body width 2.5–4.15. Elytral length/pronotal length 1.6–2.45. 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. Beetles elongate; cylindric; not necked; conspicuously waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Beetles without a rostrum. Inclination of the head strong to very strong. Eyes not strongly protuberant; without bristles; finely facetted. The labrum concealed beneath the clypeus. 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. The apical segment of the labial palps not expanded apically. Antennae very short; conspicuously elbowed; 6 segmented; with the scape much-elongated; clubbed. Antennal clubs 3 segmented, or 4 segmented. Antennal insertions visible from above, or hidden from above; not in fossae.

Cervical sclerites absent. Pronotal length/maximum pronotal width 1.05–1.67. The pronotum with lateral keels (pronotal carinae), or without lateral keels; keels if present, incomplete. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate. The prosternal process present; interrupted, or entire; when not interrupted, complete; slightly overlapping the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities closed behind externally; broadly closed; medianly confluent, or quite widely separated; circular to longer than wide; 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 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; not shaped posteriorly to receive the femur. Tarsal segmentation formula 5, 5, 5. The tarsi without bilobed segments; without ‘hidden’ segments (the third segment not being bilobed and the fourth small but clearly visible; tarsi usually long, the basal segment longer than the others combined). Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous; the penultimate segment distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 1.55–2.95. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite. 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, 6–7, or 8. Scutellary striole absent. Wings well developed. Wings without an anal lobe. Wings without a medial fleck. Abdominal sternites 5; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles. The male external genitalia curculionoid.

Adult habitat, ecology. On living vegetation, or in rotting wood (tunnelling in oak, beech, ash).

Larvae. Mature larvae small to medium-sized. The larvae apodous; elongate and more or less parallel-sided, or oblong to ovate; C-shaped in lateral view, or not C-shaped. 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 1 segmented. Stemmata present, or absent; on either side of the larval head when present, 1, or 2. The larval fronto-clypeus not extended forwardly. The frontoclypeal suture between frons and clypeus indistinct or absent, or 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, or trilobed or tridentate. The maxillary palps 1 segmented, or 2 segmented. The labium without ligula between the palps, or with a short ligula between the palps, or with a ligula at least as long as the palps. Labial palps present and segmented; 1 segmented, or 2 segmented. Mesothoracic legs much reduced or absent; 0 segmented. 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 abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature.

Larvae in rotting wood, or under bark; associated with galleries in felled oak, beech and ash.

The larvae C-shaped, without legs, with small 1-segmented antennae.

Classification. Suborder Polyphaga; Superfamily Curculionoidea.

Representation in Britain and Ireland, and worldwide. About 1000 species worldwide (mostly tropical). 2 species in Britain; genera in Britain 1; Platypus. E.g., P. cylindrus (Cylindric Ambrosia Beetle).

General comments. Adults with more or less circular eyes, and the abdomen longer than the metathorax..

Illustrations. • Platypus cylindrus (Cylindric Ambrosia-beetle: bent051). • Platypus cylindrus (details, B. Ent. 051). • Platypus cylindrus: B. Ent. 051, legend+text. • Platypus cylindrus: B. Ent. 051, text cont..

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.’.