Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Scolytidae

~Curculionidae-Scolytinae.

Bark-beetles.

General appearance. 1.2–6 mm long. Body length/maximum body width 1.27–3.15. Elytral length/pronotal length 1.2–2.43. 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-oval to elongate; cylindric; not necked; conspicuously waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae.

Detailed morphology. Beetles without a rostrum. Inclination of the head strong. Eyes strongly protuberant, or not strongly protuberant; without bristles; finely facetted. The labrum concealed beneath the clypeus. Mandibles without a mola; without prosthecae. The mandibular apices simple, or bidentate or bilobed. The incisor edges of the mandibles variously simple, or with a single tooth, 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. The apical segment of the labial palps not expanded apically. Antennae very short to short; conspicuously elbowed; 3–11 segmented; with the scape much-elongated; clubbed (the club elongated). Antennal clubs 1–3 segmented. Antennal insertions hidden from above; not in fossae.

Cervical sclerites absent. Pronotal length/maximum pronotal width 0.49–1.35. The pronotum with lateral keels (pronotal carinae), or without lateral keels; keels when present, incomplete. Prothorax without notopleural sutures. Scutellum conspicuous to highly reduced, or absent; when applicable, elevated above the mesoscutum in lateral view, or not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or truncate. The prosternal process present; interrupted, or entire; when not interrupted, complete, or incomplete; falling short of the mesoventrite, or 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; medianly confluent, or narrowly separated to quite widely separated; 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 contiguous, or narrowly separated, or moderately to widely separated; not or scarcely oblique; closed laterally. Hind-leg coxae contiguous or narrowly separated, or widely separated; extending laterally to meet the elytra, or not markedly extended laterally; not shaped posteriorly to receive the femur. 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, or without ‘hidden’ segments (the fourth segment small, but generally visible; the basal segment shorter than the others together). Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous, or pseudotetramerous; the penultimate segment not distinctly shorter than the antepenultimate one, or distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytral length/maximum width across the elytra 0.7–1.9. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite. Elytra with six or more longitudinal lines of punctures, or with six or more impressed striae, 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, 6–7, or 8 to 9. Scutellary striole absent. Wings well developed, or absent or much reduced. Wings with an anal lobe, or without an anal lobe. Wings without a medial fleck. Abdominal sternites 5; comprising both fused and moveable components. Basal abdominal sternites immovably joined 2. Abdominal segment 8 apparently without functional spiracles. The male external genitalia curculionoid.

Adult habitat, ecology. Especially under bark (some serious forest pests, including the Scolytus ulmi, the notorious principal vector of Ophiostoma ulmi, the pyrenomycete causing Dutch Elm disease); phytophagous, or boring into living wood.

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae apodous; elongate and more or less parallel-sided, or oblong to ovate; C-shaped in lateral view. Body circular in cross-section. Vestiture restricted to fine hairs or setae. The larvae dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 1 segmented. Stemmata present, or absent (?); on either side of the larval head if present, 1, or 2. The larval fronto-clypeus not extended forwardly. The frontoclypeal suture between frons and clypeus indistinct or absent, or distinct. The labrum and head capsule separated by a complete suture. Labial palps present and segmented; 1 segmented, or 2 segmented (?). Mesothoracic legs much reduced or absent; 0 segmented. Visible abdominal segments 10. Tergum 9 of the abdomen entirely dorsal. The abdomen having functional spiracles on anterior segments; without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment without cerci.

Larvae under bark; phytophagous.

The larvae C-shaped, without legs, with small 1-segmented antennae.

Classification. Suborder Polyphaga; Superfamily Curculionoidea.

Representation in Britain and Ireland, and worldwide. About 6000 species worldwide; genera about 220. 57 species in Britain; genera in Britain 27; Hylesinus, Pteleobius, Scolytus, Trypodendron, etc. E.g., Hylesinus oleiperda(Rough Hylesinus); Pteleobius vittatus; Scolytus scloytus (Elm Bark Beetle); Trypodendron lineatum.

General comments. Adult antennae with short middle segments, consisting mainly of the elongated scape and club, and dorsoventrally elongate eyes..

Illustrations. • Scolytus scolytus (Elm Bark Beetle: B. Ent. 043). • Scolytus scolytus (details, B. Ent. 043). • Scolytus scolytus: B. Ent. 043, legend+text. • Scolytus scolytus: B. Ent. 043, text cont.. • Tomicus piniperda (Pine-feeding Hylesinus: B. Ent. 104). • Tomicus piniperda (details, B. Ent. 104). • Tomicus piniperda: B. Ent. 104, legend+text. • Tomicus piniperda: B. Ent. 104, text cont.. • Hylesinus oleiperda (Rough Hylesinus: B. Ent. 522). • Hylesinus oleiperda: B. Ent. 522, legend+text. • Hylesinus oleiperda: B. Ent. 522, text cont.. • Acrantus, Hylastes, Hylastinus, Hylesinus, Hylurgops, Kissophagus, Leperisinus, Phloeophthorus, Tomicus: Fowler 5, 178 (1891). • Fowler 5, 178 (1891): original legend.. • Cryphalus, Draeocaetes, Dryocoetinus, Ernoporus, Ips, Orthotomicus, Pityogenes, Pityophthorus, Xylocleptes: Fowler 5, 179 (1891). • Fowler 5, 179 (1891): original legend.. • Platypus cylindrus, Trypodendron signatum, and Xyleborus: Fowler 5, 180 (1891). • Fowler 5, 180 (1891): original legend.. • 5 Scolytus spp., with Curculionidae: Fowler 5, 177 (1891). • Fowler 5, 177 (1891): original legend.. • Pityogenes, with Curculionidae: Fowler Suppl. 20, 1913. • Fowler Suppl. 20, 1913: original legend.. • Acrantus vittatus, Xyloterus lineatum (Rye & Fowler XII6).


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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