Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


~Scarabaeidae; currently including Bolboceratidae.

Dor-, Dung-, Clock-beetles.

General appearance. 11–26 mm long. Body length/maximum body width 1.17–1.57. Elytral length/pronotal length 1.4–2.35. 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 stoutly oval to elongate-oval; dorsally strongly convex; not necked; conspicuously waisted; generally dark reddish brown or black. Upper surfaces of body glabrous or subglabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Beetles prognathous. Inclination of the head slight (the strongly projecting mandibles readily visible in dorsal views). Eyes ostensibly four (i.e., each of the pair being completely divided into upper and lower halves); not strongly protuberant; without bristles; finely facetted. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a well developed mola. 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. 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; strongly asymmetric; not elbowed; 11 segmented; clubbed. Antennal clubs tightly lamellate (circular and biconvex, but with the capacity to open fan-like); preceded by a cupule, or without a cupule. Antennal insertions hidden from above; not in fossae.

Cervical sclerites present. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.36–0.58. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Scutellum conspicuous; when applicable, elevated above the mesoscutum in lateral view, or 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 to moderately or strongly overlapping the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities closed behind externally; narrowly closed; medianly confluent, or narrowly separated; strongly transverse to 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, or more than the shortest diameter of the cavity. The mid-leg coxal cavities contiguous, or narrowly separated, or moderately to widely separated; not or scarcely oblique, 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 with no more than two setae). Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 0.75–1.1. Elytra exposing no more than part of the terminal tergite; glossy; iridescent (commonly), or not iridescent; glabrous. 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, or 12 or more. Scutellary striole present (Bolboceratidae), or absent. Wings well developed, or absent or much reduced. Wings with an anal lobe. Wings without a medial fleck. Abdominal sternites 6–7; all articulated and moveable. Abdominal segment 8 with apparently functional spiracles. The male external genitalia bilobate.

Adult habitat, ecology. Associated with dung, or in decaying plant material; coprophagous, or mycetophagous and coprophagous.

Larvae. Mature larvae small to medium-sized, or relatively large. The larvae elongate and more or less parallel-sided, or oblong to ovate; 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. Stemmata absent. The frontoclypeal suture between frons and clypeus indistinct or absent. The labrum and head capsule separated by a complete suture. Apices of the mandibles with a single lobe or tooth, or bilobed or bidentate. The maxillary palps 4 segmented. 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; 2 segmented, or 4 segmented, or 5 segmented; the tarsi 1-clawed; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen entirely dorsal. The abdomen having functional spiracles on anterior segments (biforous or bilabiate, or cribriform); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.

Larvae in dung, or in decaying plant material and in the soil; coprophagous, or consuming decaying plant material and mycetophagous.

The larvae stridulating by rubbing the mid- and hind-legs, the latter being atrophied.

Classification. Suborder Polyphaga; Infraorder Scarabaeiformia; Superfamily Scarabaeoidea.

Representation in Britain and Ireland, and worldwide. About 600 species worldwide; genera about 30. 8 species in Britain; genera in Britain 5; Anoplotrupes, Geotrupes, Odontaeus (Bolboceratidae), Trypocopris, Typhaeus. E.g., Odontaeus armiger (Many-horned Scarab); Geotrupes vernalis (Smooth Dor, or Clock-beetle).

General comments. Head and/or pronotum often conspicuously horned; the legs very powerful and heavily armed, stridulating by rubbing a file on the hind coxae over an abdominal ridge. The larvae mostly coprophagous and/or mycetophagous, in underground burrows provisioned with dung by the adults.

Illustrations. • Odontaeus armiger (Many-horned Scarab: B. Ent. 259). • Odontaeus armiger (details, B. Ent. 259). • Odontaeus armiger: B. Ent. 259, legend+text. • Odontaeus armiger: B. Ent. 259, text cont.. • Geotrupes vernalis (Smooth Dor Beetle): B. Ent. 266. • Geotrupes vernalis: B. Ent. 266, legend+text. • Geotrupes vernalis: B. Ent. 266, text cont.. • Geotrupes stercorarius, G. sylvaticus (= stercorarius), G. vernalis, Odontaeus armiger (with Scarabaeidae and Trogidae): Fowler 4, 102 (1890). • Fowler 5, 102 (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.’.