Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz



General appearance. 10–66 mm long (to 8 cm in some tropical forms). Body length/maximum body width 1.3–2.85. Elytral length/pronotal length 1.65–3.2. 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, or distinctly narrower than greatest elytral width. Beetles round to elongate-oval; 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 to strong. Eyes strongly protuberant, or not strongly protuberant; without bristles; finely facetted, or coarsely facetted. Labrum mostly moderately to heavily sclerotized. Mandibles with a reduced mola, or without a mola; with well developed prosthecae to without prosthecae. The mandibular apices simple, or bidentate or bilobed, or multidentate or multilobed. The incisor edges of the mandibles simple, or with a single tooth, or with two or more teeth. 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 to about half the insect's head to tail length; strongly asymmetric; conspicuously elbowed; 8 segmented, or 10 segmented; with the scape much-elongated; clubbed. Antennal clubs openly lamellate (not tightly so); preceded by a cupule, or without a cupule. Antennal insertions hidden from above; not in fossae.

Cervical sclerites present. Prothorax shorter than wide to about as long as wide. Pronotal length/maximum pronotal width 0.43–0.9. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax at its widest 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 to absent; when applicable, not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or 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 closed behind externally; broadly closed; narrowly separated, or quite widely separated; strongly 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 (mostly), or markedly oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; extending laterally to meet the elytra. 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; with an empodium between them (this sometimes with three or more setae), or without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 0.87–1.95. Elytra exposing no more than part of the terminal tergite; glossy; striate, or without striae (usually). 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, 6–7, or 8 to 10. Scutellary striole absent. Wings well developed, or absent or much reduced. Wings 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. Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles. The male external genitalia trilobate (Sinodendron only), or bilobate.

Adult habitat, ecology. Phytophagous, or consuming decaying plant material (e.g., feeding on sap, fruits or flowers?).

Larvae. Mature larvae small to medium-sized to relatively large. The larvae elongate and more or less parallel-sided; C-shaped in lateral view. 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, or 4 segmented. Stemmata absent. The frontoclypeal suture between frons and clypeus distinct. The labrum and head capsule separated by a complete suture. Apices of the mandibles bilobed or bidentate, or trilobed or tridentate. The maxillary palps 4 segmented. The labium without ligula between the palps. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented (the coxae equipped on the posterior face with a stridulatory file); 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 (these cribriform); 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, or in the soil (e.g., under logs); consuming decaying plant material.

The stridulatory file on the mid-coxae can be detected by scraping a fine needle along the posterior face.

Classification. Suborder Polyphaga; Infraorder Scarabaeiformia; Superfamily Scarabaeoidea.

Representation in Britain and Ireland, and worldwide. About 1200 species worldwide; genera about 130. 4 species in Britain; genera in Britain 4; Dorcus, Lucanus, Platycerus, Sinodendron. E.g., Lucanus cervus (Stag Beetle); Platycerus caraboides (Blue Lucanus, extinct in Britain?); Sinodendron cylindricum (Cylindrical Lucanus).

General comments. The adult males of some species can exhibit enormous mandibles, which may vary greatly in size relative to the rest of the insect, the variation perhaps reflecting nutritive conditions in the larval stage. Tarsi sometimes with fewer than three segments in non-British species.

Illustrations. • Lucanus cervus (Stag Beetle: B. Ent. 490). • Lucanus cervus (detail: B. Ent. 490). • Lucanus cervus: B. Ent. 490, legend+text. • Lucanus cervus: B. Ent. 490, text cont.. • Platycerus caraboides (Blue Lucanus, extinct in Britain): B. Ent. 274. • Platycerus caraboides: B. Ent. 274, legend+text. • Platycerus caraboides: B. Ent. 274, text cont.. • Sinodendron cylindricum (Cylindrical Lucanus: B. Ent. 478). • Sinodendron cylindricum: B. Ent. 478, legend+text. • Sinodendron cylindricum: B. Ent. 478, text cont.. • Dorcus papallelipipedus, Lucanus cervus, Platycerus caraboides, Sinodendron cylindricum: Fowler 4, 99 (1890). • Fowler 4, 99 (1890): 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.’.