Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz



Sexton Beetles, Carrion Beetles.

General appearance. 9–30 mm long. Body length/maximum body width 1.45–2.7. Elytral length/pronotal length 1.65–2.95. 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. Body noticeably widest immediately behind the thorax, or noticeably widest at the rear (?). Beetles elongate-oval to elongate; dorsally flattened; not necked; somewhat waisted to conspicuously waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Eyes 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, or with a reduced mola; with well developed prosthecae. The mandibular apices simple. The incisor edges of the mandibles simple (Nicophorinae), or with a single tooth (Silphinae). 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; 11 segmented; gradually expanding towards the apex, or clubbed. Antennal clubs 3 segmented; preceded by a cupule, or without a cupule. Antennal insertions visible from above.

Cervical sclerites present. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.57–0.9. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate. The prosternal process present; incomplete; falling short of 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; medianly confluent; 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 (Silphinae), or more than the shortest diameter of the cavity (Nicophorinae). The mid-leg coxal cavities narrowly separated, or moderately to widely separated; not or scarcely oblique, or markedly oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; not markedly extended laterally. 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 (sometimes with bilobed segments). 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 as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 0.97–1.47. Elytra meeting along the length of the mid-line; covering most to all of the abdomen, or short, exposing several terminal abdominal tergites; exposing no more than part of the terminal tergite, or at least three complete abdominal tergites; truncate. 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 without a medial fleck. Abdominal sternites 6–7; all articulated and moveable. Abdominal segment 8 with apparently functional spiracles. The male external genitalia staphylinoid.

Adult habitat, ecology. Not predacious (mostly), or predacious (some Silphinae); especially associated with carrion, or associated with fungi; mostly necrophagous, or consuming decaying plant material, or mycetophagous.

Larvae. Mature larvae small to medium-sized to relatively large. The larvae elongate and more or less parallel-sided, or oblong to ovate. Body somewhat flattened to strongly flattened. Vestiture restricted to fine hairs or setae, or not restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized, or dorsally only very lightly pigmented or sclerotized; ventrally more or less heavily pigmented, or ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present; on either side of the larval head when present, 1, or 6. 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. 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 entirely dorsal. The abdomen having functional spiracles on anterior segments (these annular); with anterior and 8th-segmental spiracles borne at the ends of a series of spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 bearing a pair of processes, each with an apical spiracle, or without amature. The last abdominal segment with cerci.

Larvae predacious (some Silphinae), or not predacious; in living vegetation, or in decaying plant material (some Silphinae), or in carrion (Nicophorinae, which inhabit small animal carcasses buried in readiness for them by the adults); necrophagous (Nicophorinae and some non-predatory Silphinae), or phytophagous (some Silphinae).

Classification. Suborder Polyphaga; Infraorder Staphyliniformia; Superfamily Staphilinoidea.

Representation in Britain and Ireland, and worldwide. About 190 species worldwide. 23 species in Britain; genera in Britain 7; Aclypea, Blitophaga, Dendroxena, Necrodes, Nicrophorus, Oiceoptoma, Silpha, Thanatophilus. E.g., Necrodes littoralis (Bent-legged Silpha); Necrophorus germanicus (Black-horned Grave-digger); Necrophorus vespilloides (Sexton Beetle); Blitophaga opaca.

General comments. The head much narrower than the thorax; the 4 basal abdominal tergites soft; the fore coxae with the trochanters exposed. Including species well known for burying corpses of small animals to serve as food for the larvae..

Illustrations. • Aclypea opaca: B. Ent. 742. • Aclypea opaca: B. Ent. 742, legend+text. • Aclypea opaca: B. Ent. 742, text cont.. • Aclypea opaca (Janson 101). • Necrodes littoralis (Bent-legged Silpha: B. Ent. 334). • Necrodes littoralis (details, B. Ent. 334). • Necrodes littoralis: B. Ent. 334, legend+text. • Necrodes littoralis: B. Ent. 334, text cont.. • Nicrophorus germanicus (Black-horned Grave-digger: B. Ent. 071). • Nicrophorus germanicus: B. Ent. 071, legend+text. • Nicrophorus germanicus: B. Ent. 071, text cont.. • Aclypea retinaculata, Dendroxena quadrimacula, Necrodes littoralis, Nicrophorus (6 spp.), Silpha (3 spp.): Fowler 3, 73 (1889). • Fowler 3, 73 (1889): original legend.. • Aclypea, Oiceoptoma, Silpha, Thanatophilus (3 spp.), with Silphidae: Fowler 3, 74 (1889). • Fowler 3, 74 (1889): original legend.. • Nicrophorus vespilloides (Sexton Beetle: Rye & Fowler VI1).

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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.’.