Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Byturidae

Fruitworm beetles, Raspberry beetle.

General appearance. 3.5–5 mm long. Body length/maximum body width 1.45–2.72. Elytral length/pronotal length 3–3.5. 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. Beetles elongate; cylindric; not necked; somewhat waisted to conspicuously waisted; deep yellow, covered with fine yellow pubescence. Upper surfaces of body non-glabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Beetles not prognathous. Inclination of the head strong. 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 well developed mola. The mandibular apices simple, or bidentate or bilobed. The incisor edges of the mandibles 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 to short; 11 segmented; clubbed. Antennal clubs 3 segmented.

Cervical sclerites present. Pronotal length/maximum pronotal width 0.45–0.75. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax with neither produced front corners nor serrated sides. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly broadly rounded or obtusely angulate, or truncate. 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 open behind externally, or closed behind externally (?); if open, narrowly open; narrowly separated; strongly transverse; with narrow lateral extensions; internally closed by a slender bar, or broadly closed internally. 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; markedly oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; not markedly extended laterally. Tarsal segmentation formula ostensibly 5, 5, 4, or 4, 4, 4 (hard to interpret: the tarsi are velvety beneath, with five segments; the first and fourth segments are very small, with the latter hidden between the lobes of the third, and the fifth is as long as the rest together). The tarsi exhibiting bilobed segments (the second and third segments produced into long lappets); with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth and with a tiny basal segment that is hard to detect. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; ambiguously pentamerous, or pseudotetramerous (the penultimate one), 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 one-toothed or bifid (bent, with a strong tooth at the base beneath). Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 1.02–2.1. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite. The pygidium at least partly exposed beyond the long elytra. Elytra not truncate; non-glabrous (covered with silky yellow hairs). Elytra with six or more longitudinal lines of punctures, or apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae; the lines per elytron when more than five, 10. Scutellary striole present. Wings well developed. Wings with an anal lobe. Wings with a medial fleck; the medial fleck 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. On living vegetation and associated with flowers.

Larvae. Mature larvae 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; 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. 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 extending to the underside. The abdomen having functional spiracles on anterior segments (these annular-biforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci.

Larvae phytophagous (in fruits of raspberries and blackberries, including the pest ‘raspberry beetle’ (Byturus tomentosus)).

Classification. Suborder Polyphaga; Superfamily Cucujoidea.

Representation in Britain and Ireland, and worldwide. About 25 species worldwide (holarctic). 2 species in Britain; genera in Britain 1; Byturus. E.g., Byturus tomentosus.

General comments. Unwin represents the modified tarsi as “4,4,4 with some bilobed segments”, while Imms and Lawrence et al. settle for 5,5,5 .... Medial fleck of hindwing partly bisected by a vein.

Illustrations. • Byturus tomentosus: B. Ent. 618. • Byturus tomentosus: B. Ent. 618, legend+text. • Byturus tomentosus: B. Ent. 618, text cont.. • Byturus tomentosus (with Cucujidae, Silvanidae etc.): Fowler 3, 93 (1889). • Fowler 3, 93 (1889): original legend.. • Byturus tomentosus (Janson 90).


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’.

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