British insects: the families of Coleoptera


L. Watson and M. J. Dallwitz


= Lymexylonidae; including Atractoceridae.

Timber-borers, Ship-timber beetles, Ambrosia beetles.

General appearance. 7–18 mm long. Body length/maximum body width 4.05–12.2. Elytral length/pronotal length 1.5–5.25. 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 to slender; conspicuously necked to not necked; somewhat waisted. Upper surfaces of body non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Eyes strongly protuberant; without bristles; finely facetted. Antennae short; 11 segmented. Antennal scape not swollen. Antennae filiform (or fusiform), or serrate. Antennal insertions visible from above, or hidden from above. Mandibular prosthecae well developed, or absent. Prothorax longer than wide. Pronotal length/maximum pronotal width 0.75–1.5. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’, or attached externally, in the absence of procoxal cavities. The mid-leg coxae countersunk in ‘mesocoxal cavities’; cavities open laterally. Hind-leg coxae extending laterally to meet the elytra (Lymexylon), or not markedly extended laterally (Hyecoetus). 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 claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple; with an empodium between them (this sometimes with three or more setae). Hind tarsi with as many segments as the mid-tarsi; 5-segmented. Elytral length/maximum width across the elytra 1.45–4.67. Elytra individually distinctly tapered to their apices to not individually tapered; not meeting along the full length of the mid-line (at least, narrowly separated towards their tips); fairly short, exposing several terminal abdominal tergites (in the British representatives); exposing no more than part of the terminal tergite to at least three complete abdominal tergites (the abdominal tip pointed); truncate; soft. Scutellary striole absent. Elytra non-glabrous. Wings well developed. Exposed abdominal sternites 5–7; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles.

Adult habitat, ecology. Boring into living wood (causing fungal infections on which the larvae feed), or boring into dead wood.

Larvae. Mature larvae small to medium-sized to relatively large. The larvae elongate and more or less parallel-sided. 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 3 segmented. Stemmata absent. 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. The maxillary palps 3 segmented. The labium with a short ligula between the palps, or with a ligula at least as long as the palps. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented; 5 segmented; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen extending to the underside. The abdomen having functional spiracles on anterior segments (these annular or annular-multiforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.

Larvae in tunnels bored in the wood of weakened trees; mycetophagous.

The larvae boring into living and decaying wood; elongate, thin, cylindrical with short but well developed legs, prognathous with 3-segmented antennae, the sclerotized pronotum partially hooding the head.

Classification. Suborder Polyphaga; Superfamily Lymexyloidea.

Worldwide and British representation. About 40 species worldwide; genera 7. 2 species in Britain; genera in Britain 2; Hylecoetus, Lymexylon. E.g., H. dermestoides; L. navale (Windsor Wood-borer).

General comments. Elongate, soft bodied beetles. Worldwide variation ranges from forms with elytra so short that they do not reach the abdomen, to others in which they cover all except the terminal tergite. In common with Cantharidae, Meloidae, Lampyridae, Lycidae, some Dermestidae, some Melyridae and some Staphylinidae, the undersides of some lymexylids lack the usual procoxal cavities.

Illustrations. • Hylecoetus dermestoides: B. Ent. 654. • Hylecoetus dermestoides: B. Ent. 654, legend+text. • Hylecoetus dermestoides: B. Ent. 654, text cont.. • Hylecoetus dermestoides (Rye & Fowler IX6). • Hylecoetus dermestoides (Janson 162). • Lymexylon navale (Windsor Wood-borer: B. Ent. 382). • Lymexylon navale (details, B. Ent. 382). • Lymexylon navale: B. Ent. 382, legend+text. • Lymexylon navale: B. Ent. 382, text cont.. • Hylecoetus dermestoides and Lymexylon navale (with Ptinidae, Cleridae, etc.): Fowler 4, 116 (1890). • Fowler 4, 116 (1890): original legend.

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. British insects: the families of Coleoptera. Version: 25th July 2012.’.