Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Tetratomidae

Melandryidae p.p.

Polypore fungus beetles.

General appearance. 3–4 mm long. Body length/maximum body width 1.9–2.36. Elytral length/pronotal length 3–5.05. 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 rather cylindric; not necked; head and elytra black, thorax yellow; exhibiting bright ‘warning colours’. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Eyes strongly protuberant; without bristles; coarsely facetted. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a well developed mola; with well developed prosthecae. The mandibular apices bidentate or bilobed. 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 short; 11 segmented; clubbed. Antennal clubs 4 segmented (elongate). Antennal insertions visible from above, or hidden from above.

Cervical sclerites present. Pronotal length/maximum pronotal width 0.45–0.7. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly broadly rounded or obtusely angulate. The prosternal process complete; slightly 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; narrowly separated; slightly transverse; with narrow 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; not or scarcely oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; not markedly extended laterally; not shaped posteriorly to receive the femur. Tarsal segmentation formula 5, 5, 4. 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. Hind tarsi with one segment fewer than the mid-tarsi; 4-segmented.

Elytral length/maximum width across the elytra 1.45–1.83. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite; not truncate; glossy. Elytra apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae. Scutellary striole absent. Wings well developed. Wings without an anal lobe. Wings with a medial fleck; the medial fleck not bisected by a vein. Abdominal sternites 5; all articulated and moveable, or comprising both fused and moveable components. Basal abdominal sternites immovably joined when present, 2. Abdominal segment 8 apparently without functional spiracles. The male external genitalia tenebrionoid.

Adult habitat, ecology. Not predacious (?); associated with fungi (especially with fruit bodies of wood-rotting fungi); mycetophagous.

Larvae. Mature larvae small to medium-sized to relatively large. The larvae elongate and more or less parallel-sided. Body circular in cross-section, or somewhat flattened. Vestiture restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized, or dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present; on either side of the larval head 5. The frontoclypeal suture between frons and clypeus indistinct or absent. The labrum and head capsule separated by a complete suture. Apices of the mandibles bilobed or bidentate. The maxillary palps 3 segmented. The labium 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 extending to the underside. The abdomen having functional spiracles on anterior segments (these annular-biforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci.

Larvae associated with fungi; mycetophagous (commonly consuming fruit bodies of lignicolous toadstools and polypores).

Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Tenebrionoidea.

Representation in Britain and Ireland, and worldwide. About 30 species worldwide. 3 species in Britain; genera in Britain 1; Tetratoma. E.g., T. ancora (Black-and-yellow Tetratoma).

General comments. The elytra punctured.

Illustrations. • Tetratoma ancora (Black-and-yellow Tetratoma: B. Ent. 123). • Tetratoma ancora (details, B. Ent. 123d). • Tetratoma ancora: B. Ent. 123, legend+text. • Tetratoma ancora: B. Ent. 123, text cont.. • Tetratoma ancora, T. desmaresti and T. fungorum, with Tenebrionidae: Fowler 5, 145 (1891). • Fowler 5, 145 (1891): 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. delta-intkey.com’.

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