Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


General appearance. 1.8–2.3 mm long. Body length/maximum body width 1.83–2.24. Elytral length/pronotal length 3.05–3.7. Base of prothorax distinctly narrower than the combined elytral bases. Greatest prothoracic width distinctly narrower than greatest elytral width. Body noticeably widest at the rear. Beetles oval to elongate-oval; dorsally flattened to dorsally somewhat convex; not necked; conspicuously waisted; decidedly short-legged. Upper surfaces of body non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Inclination of the head slight. Eyes strongly protuberant; bristly; finely facetted. Ocelli present; paired. The frons without a transverse ridge between the eyes. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a reduced mola; with reduced 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. The apical segment of the labial palps not expanded apically. Antennae short (about 0.25 of the beetle’s length); 11 segmented; clubbed. Antennal clubs 3 segmented; without a cupule. Antennal insertions visible from above.

Cervical sclerites present. Prothorax much shorter than wide. Pronotal length/maximum pronotal width 0.61–0.81. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax with notopleural sutures. Scutellum conspicuous; elevated above the mesoscutum in lateral view; anteriorly simple; posteriorly broadly rounded or obtusely angulate. The prosternal process present; complete; falling short of the mesoventrite to slightly overlapping the mesoventrite. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally; narrowly open; narrowly separated; 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. The mid-leg coxal cavities contiguous, or narrowly separated; not or scarcely oblique (circular to slightly transverse); open laterally. Hind-leg coxae contiguous or narrowly separated; not much enlarged; extending laterally to meet the elytra. Tarsal segmentation formula 4, 4, 4. The tarsi exhibiting bilobed segments; with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pseudotetramerous; the penultimate segment distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 1.4–1.76. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite. The pygidium entirely concealed by the ends of the elytra even when viewed from behind. Elytra not truncate; striate (with 10 rows of punctures). Elytra with six or more longitudinal lines of punctures; the lines per elytron 10. Scutellary striole present. Elytra with epipleura to without epipleura (?). Elytral epipleura if present, falling short of the elytral tips. Wings with an anal lobe. Wings without a medial fleck. Abdominal sternites 5; comprising both fused and moveable components (4 articulated with or connate with 3 and 5). Abdominal segment 8 with apparently functional spiracles. The male external genitalia trilobate.

Adult habitat, ecology. The British representative predacious (on woolly aphids); on living vegetation (on conifers).

Larvae. Mature larvae minute (less than 3 mm long) to 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 heavily pigmented or sclerotized, or dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present; on either side of the larval head 6. The frontoclypeal suture between frons and clypeus indistinct or absent to distinct. The labrum and head capsule separated by a complete suture. Apices of the mandibles bilobed or bidentate. 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; 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 without amature. The last abdominal segment without cerci.

Larvae predacious (on woolly aphids of conifers); in living vegetation.

Classification. Suborder Polyphaga; Infraorder Bostrichiformia; Superfamily Bostrichoidea.

Representation in Britain and Ireland, and worldwide. 1 species in Britain (L. erichsonii); genera in Britain 1; Laricobius.

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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.’.