Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Sphaeritidae

General appearance. 5.5–6.5 mm long. Body length/maximum body width 1.6–1.7. Elytral length/pronotal length 2.35–2.48. 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 oval to elongate-oval; not necked; conspicuously waisted. Upper surfaces of body glabrous or subglabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Eyes 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 reduced mola. The mandibular apices simple. The incisor edges of the mandibles 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; 11 segmented; clubbed. Antennal clubs 3 segmented; preceded by a cupule. Antennal insertions visible from above.

Cervical sclerites present. Pronotal length/maximum pronotal width 0.52–0.58. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax without notopleural sutures. Scutellum conspicuous; elevated above the mesoscutum in lateral view; anteriorly simple; posteriorly broadly rounded or obtusely angulate. The prosternal process complete; falling short of the mesoventrite to slightly overlapping the mesoventrite. Metaventrite with a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally; narrowly open; narrowly separated; strongly 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, or moderately to widely separated; not or scarcely 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. 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 1.1–1.2. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite; glabrous; striate (each with 9 longitudinal rows of fine puntures, by contrast with Histeridae). Elytra with six or more longitudinal lines of punctures; the lines per elytron 10. Scutellary striole absent. Wings well developed. Wings with an anal lobe. Wings without a medial fleck. Abdominal sternites 5; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles. The male external genitalia histeroid.

Adult habitat, ecology. Associated with fungi (in coniferous woodland in Scotland).

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae elongate and more or less parallel-sided. Body somewhat flattened. 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 completely fused, with no suture apparent. Apices of the mandibles with a single lobe or tooth. The maxillary palps 4 segmented. The labium without 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 biforous or bilabiate); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci.

Larvae feeding habits seemingly unknown.

Classification. Suborder Polyphaga; Infraorder Staphyliniformia; Superfamily Histeroidea.

Representation in Britain and Ireland, and worldwide. 4 species worldwide (widespread temperate); genera 1 (Sphaerites). 1 species in Britain (S. glabratus); genera in Britain 1; Sphaerites.

General comments. Small oval, black beetles with a slight bluish-green sheen.

Illustrations. • Sphaerites glabratus (from Joy). Sphaerites glabratus. • Sphaerites glabratus, with Leiodidae: Fowler 3, 75 (1889). • Fowler 3, 74 (1889): 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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