Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Trogossitidae

Including Lophocateridae, Ostomatidae, Ostomidae, Temnochilidae, Temnoscheilidae.

Bark-gnawing beetles.

General appearance. 5–11 mm long. Body length/maximum body width 1.25–7.65. Elytral length/pronotal length 1.75–4.58. 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, or slender; dorsally flattened; not necked; conspicuously 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.

Detailed morphology. Beetles prognathous. Inclination of the head slight. Eyes strongly protuberant, or not strongly protuberant; bristly, or without bristles. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a well developed mola, or with a reduced mola, or without a mola; with well developed prosthecae to without prosthecae. The mandibular apices simple, or bidentate or bilobed. The incisor edges of the mandibles simple, or with a single tooth, or with two or more teeth (some Trogossitinae only). 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 to short; 10 segmented. Antennal scape not swollen. Antennae clubbed. Antennal clubs 1 segmented, or 3 segmented. Antennal insertions visible from above, or hidden from above; not in fossae.

Cervical sclerites present. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.3–1.52. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax at its widest markedly narrower than the adjoining part of the abdomen to not markedly narrower than the adjoining part of the abdomen; having the front corners produced, or with serrated sides, or with neither produced front corners nor serrated sides. Prothorax without notopleural sutures. Scutellum conspicuous, or highly reduced to absent (some Trogossitinae); when applicable, not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or truncate. The prosternal process complete; slightly overlapping the mesoventrite. Metaventrite with a transverse groove, or without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally, or closed behind externally (some Trogossitinae); broadly open to narrowly open, or broadly closed (Trogossitinae); narrowly separated, or quite widely separated; strongly transverse, or slightly transverse; 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; open 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, 4. The tarsi without bilobed segments; with a tiny basal segment that is hard to detect. Front tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented (actually 5 segmented, with a tiny basal segment). Mid-leg tarsi 4-segmented (ostensibly), or 5-segmented (actually 5); 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, or one-toothed or bifid; with an empodium between them (this bisetose). Hind tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented.

Elytral length/maximum width across the elytra 0.82–3.3. Elytra meeting along the length of the mid-line; covering most to all of the abdomen; exposing no more than part of the terminal tergite, or at least three complete abdominal tergites; truncate, or not truncate. Elytra with six or more longitudinal lines of punctures (some Lophocaterinae), or with six or more impressed striae (some Trogossitinae), 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, or absent or much reduced. Wings with an anal lobe, or without an anal lobe. Wings without a medial fleck. Abdominal sternites 5–6; all articulated and moveable, or comprising both fused and moveable components. Basal abdominal sternites immovably joined when present, 2, or 4–6. Abdominal segment 8 apparently without functional spiracles. The male external genitalia cucujiform.

Adult habitat, ecology. Land-dwellers; variously predacious, or not predacious; on living vegetation and associated with flowers, or in rotting wood, or associated with fungi, or in dried plant material, or in stored plant products (e.g., in stored cereals); commonly consuming decaying plant material, or consuming rotting wood, or mycetophagous.

Larvae. Mature larvae small to medium-sized. The larvae elongate and more or less parallel-sided. Body circular in cross-section to strongly flattened. Vestiture restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present, or absent (some Peltinae); on either side of the larval head when present, 3–6. The frontoclypeal suture between frons and clypeus indistinct or absent (mostly), or distinct (Thymalus). The labrum and head capsule separated by a complete suture. Apices of the mandibles bilobed or bidentate. The maxillary palps 2 segmented (Rentoniinae), or 3 segmented (mostly), or 4 segmented (some Peltinae). 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; 5 segmented; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen entirely dorsal, or extending to the underside. The abdomen having functional spiracles on anterior segments (these consistently annular-biforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci (usually), or without cerci (some Rentoniinae only).

Larvae predacious (or facultatively so), or not predacious; in divers habitats, in rotting wood, in dried plant material, under bark, and associated with fungi (often in tunnels of wood boring insects, and commonly in bracket fungi).

The larvae, elongate, whitish, subcylindrical or tapered towards the head, head exserted, with several pairs of ocelli, the pronotum and segment 9 sclerotized.

Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Cleroidea.

Representation in Britain and Ireland, and worldwide. About 600 species worldwide. 2 species in Britain; genera in Britain 2; Nemozoma, Tenebroides. E.g., Nemozoma elongatum (Elongated Nemosoma); Tenebroides mauritanicus.

General comments. Beetles without erect bristles, though sometimes clothed with scales; the head cleft in front and the eyes borne well in front of the thorax..

Illustrations. • Nemozoma elongatum (Elongated Nemosoma: B. Ent. 327). • Nemozoma elongatum (details, B. Ent. 327). • Nemozoma elongatum: B. Ent. 327, legend+text. • Nemozoma elongatum: B. Ent. 327, text cont.. • Tenebroides mauritanicus: B. Ent. 734. • Tenebroides mauritanicus: B. Ent. 734, legend+text. • Tenebroides mauritanicus: B. Ent. 734, text cont.. • Tenebroides mauritanicus (Janson 226). • Nemozoma elongatum and Tenebroides mauritanicus (with Rhizophagidae, Merophysiidae, etc.): Fowler 3, 91 (1889). • Fowler 3, 91 (1889): 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. Insects of Britain and Ireland: the families of Coleoptera. Version: 16th May 2016. delta-intkey.com’.

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