Insects of Britain and Ireland: the families of Coleoptera
Minute Hooded Beetles.
General appearance. 0.5–1 mm long. Body length/maximum body width 1.25–2.4. Elytral length/pronotal length 1.45–4.16. 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. Body noticeably widest immediately behind the thorax, or not noticeably widest either behind the thorax, or at the rear. Beetles broadly oval; dorsally somewhat convex; not necked; not waisted; decidedly short-legged; brown, yellow, reddish yellow or pitchy. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.
Detailed morphology. Beetles not prognathous. The head very small, covered by the thorax. Inclination of the head slight to strong. Eyes strongly protuberant, or not strongly protuberant; without bristles. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles variously with a well developed mola, or without a mola (according to group); with well developed prosthecae, or without prosthecae. The mandibular apices variously simple, or bidentate or bilobed, or multidentate or multilobed. The incisor edges of the mandibles simple, or with two or more teeth. The maxillae with a single apical structure additional to the palp. The apical segment of the maxillary palps cylindrical to fusiform (mostly), or somewhat expanded and truncate to subtriangular (some Corylophini). The apical segment of the labial palps not expanded apically. Antennae very short to short; 9–11 segmented; not hairy; without a much-elongated scape. Antennal scape swollen (triangular). Antennae clubbed. Antennal clubs loosely 3 segmented. Antennal insertions visible from above, or hidden from above; not in fossae.
Cervical sclerites present, or absent. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.3–0.8. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen; with neither produced front corners nor serrated sides. Prothorax without notopleural sutures. Scutellum conspicuous (usually), or highly reduced (Orthoperinae); not elevated; anteriorly simple; posteriorly 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; narrowly closed to broadly closed; narrowly separated, or narrowly separated to quite widely separated; strongly transverse, or slightly transverse, or circular to longer than wide; without lateral extensions; broadly closed internally. 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 moderately to widely separated; not or scarcely oblique; open laterally (Orthoperinae), or closed laterally (usually). Hind-leg coxae widely separated; widely separated, and not markedly extended laterally; not shaped posteriorly to receive the femur. Tarsal segmentation formula 4, 4, 4. The tarsi without bilobed segments (but the third segment lobed beneath); with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth, or without hidden segments. Front tarsi with as many segments as the mid-tarsi; 4-segmented. Mid-leg tarsi 4-segmented; tetramerous, or pseudotrimeous; the penultimate segment distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple, or one-toothed or bifid; 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; 4-segmented.
Elytral length/maximum width across the elytra 0.8–1.77. Elytra exposing no more than part of the terminal tergite to at least one but fewer than three complete abdominal tergites; glossy, or dull; non-glabrous (hairy); without striae. 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 falling short of the elytral tips. Wings well developed, or absent or much reduced; fringed with long hairs on the hind margin, or not fringed. Wings without an anal lobe. Wings with a medial fleck, or without a medial fleck; the medial fleck when present, not bisected by a vein. Abdominal sternites 5–6; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles. The male external genitalia cucujiform.
Adult habitat, ecology. In decaying plant material, in rotting wood, and under bark (commonly in rotting vegetable material); consuming decaying plant material and mycetophagous (on spores and mycelium).
Larvae. Mature larvae minute (less than 3 mm long). The larvae oblong to ovate. Body somewhat flattened (mostly), or strongly flattened (Peltinodinae, Rypobiinae). Vestiture not restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized, or dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 2 segmented, or 3 segmented. Stemmata present; on either side of the larval head 2. 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, or trilobed or tridentate. The maxillary palps 2 segmented, or 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 (annular); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.
Larvae in decaying plant material, in rotting wood, and under bark; probably mainly mycetophagous (on fungal spores and mycelium).
Classification. Suborder Polyphaga; Superfamily Cucujoidea.
Representation in Britain and Ireland, and worldwide. About 290 species worldwide; genera 27. 10 species in Britain; genera in Britain 4; Corylophus, Orthoperus, Rypobius, Sericoderus. E.g., Corylophus cassidioides.
General comments. Minute beetles, shiny, broadly ovate and only slightly convex, shiny.
Illustrations. • Corylophus cassidioides, Orthopterus atomus, O. atomarius, Sericoderus lateralis (with Ptiliidae and Sphaeriidae): Fowler 3, 80 (1889). • Fowler 3, 80 (1889): original legend.. • Corylophus cassidioides (Rye & Fowler XVI1).
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’.