Insects of Britain and Ireland: the families of Coleoptera
General appearance. 1.2–3 mm long. Body length/maximum body width 1.38–2.77. Elytral length/pronotal length 1.2–3. 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 elongate; cylindric; not necked; somewhat waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; exhibiting stiff, erect, dark bristles, or not bristly; with neither scales nor scale-like setae.
Detailed morphology. Beetles prognathous. Inclination of the head slight. Eyes strongly protuberant; bristly, or 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; without prosthecae. The mandibular apices bidentate or bilobed. The incisor edges of the mandibles simple. The maxillae with distinct galea and lacinia apically to the palp. The apical segment of the maxillary palps cylindrical to fusiform, or somewhat expanded and truncate to subtriangular. The apical segment of the labial palps not expanded apically. Antennae short; 8–11 segmented. Antennal scape not swollen. Antennae clubbed. Antennal clubs 3 segmented (elongate, the segments obviously separated). Antennal insertions visible from above, or hidden from above; not in fossae.
Cervical sclerites absent. Prothorax about as long as wide. Pronotal length/maximum pronotal width 0.55–0.95. 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, or highly reduced; elevated above the mesoscutum in lateral view (Ciinae), or not elevated (Sphindociinae); anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate. The prosternal process present, or absent; when present, interrupted, or entire; when present and not interrupted, complete, or incomplete; when present and not interrupted, falling short of the mesoventrite to 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, or closed behind externally; narrowly open, or narrowly closed; medianly confluent, or narrowly separated to quite widely separated; 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. The mid-leg coxal cavities contiguous, or 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 4, 4, 4, or 3, 3, 3. The tarsi without bilobed segments; without hidden segments. Front tarsi with as many segments as the mid-tarsi; 3-segmented, or 4-segmented (with segments 1–3 short). Mid-leg tarsi 3-segmented, or 4-segmented (with segments 1–3 short); tetramerous, or trimerous; 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), or without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 3-segmented, or 4-segmented (with segments 1–3 short).
Elytral length/maximum width across the elytra 0.88–2.08. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite; without striae (punctures randomly distributed, at least over the forward part). Elytra apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae. Scutellary striole absent. Elytra with epipleura. Elytral epipleura reaching to the tips of the elytra. Wings well developed, or absent or much reduced. 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. In rotting wood, under bark, and associated with fungi (commonly in bracket fungi in trees); mycetophagous.
Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized (generally very small in British representatives). The larvae oblong to ovate. 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 2 segmented. Stemmata present, or absent; on either side of the larval head when present, 1–5. 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 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; 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); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci, or without cerci.
Larvae not predacious; in rotting wood, under bark, and associated with fungi (cf. the adults); mycetophagous.
Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Tenebrionoidea.
Representation in Britain and Ireland, and worldwide. Genera about 50 (? - mostly in warm regions). 22 species in Britain; genera in Britain 4; Cis, Octotemnus, Rhopalodontus, Sulcacis. E.g., Cis bidentatus (Double-horned Cis).
General comments. Minute, cylindrical beetles, somewhat resembling Curculionidae-Scolitinae, but the three-segmented antennal club is less compact.
Illustrations. • Cis bidentatus (Double-horned Cis: B. Ent. 402). • Cis bidentatus (details, B. Ent. 402). • Cis bidentatus: B. Ent. 402, legend+text. • Cis bidentatus: B. Ent. 402, legend cont.. • Cis (5 spp.), Ennearthron, Octotemnus, Sulcacis (with unrelated taxa): Fowler 4, 119 (1890). • Fowler 4, 119 (1890): original legend.. • Cis dentatus, with Cerambycidae etc.: Fowler Suppl. 16, 1913. • Fowler Suppl. 16, 1913: original legend..
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
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’.