Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


= Platystomidae; including Bruchelidae, Urodontidae.

Fungus weevils.

General appearance. 2.5–10 mm long. Body length/maximum body width 1.4–3. Elytral length/pronotal length 1.5–3. Base of prothorax not or scarcely narrower than the combined elytral bases, or distinctly 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; not necked; somewhat waisted, or 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 equipped with a rostrum (this short and flattened, by contrast with that of weevils). Inclination of the head slight to very 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 with a well developed mola, or with a reduced mola, or without a mola; without prosthecae. The mandibular apices simple, or bidentate or bilobed. The incisor edges of the mandibles simple, or with a single tooth. The maxillae with distinct galea and lacinia apically to the palp. The maxillary palps normal, flexible; apical segment of the maxillary palps cylindrical to fusiform. The apical segment of the labial palps not expanded apically. Antennae short to long, but not exceeding the insect’s head to tail length; not elbowed; 9–11 segmented; without a much-elongated scape. Antennal scape not swollen. Antennae filiform, or clubbed. Antennal clubs when present, 3 segmented. Antennal insertions visible from above, or hidden from above; not in fossae.

Cervical sclerites absent. Prothorax shorter than wide to longer than wide. Pronotal length/maximum pronotal width 0.4–1.15. The pronotum with lateral keels (pronotal carinae), or without lateral keels; keels when present, complete, or incomplete. Posterior edge of the pronotum not crenulate. Prothorax at its widest markedly narrower than the adjoining part of the abdomen, or not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Scutellum conspicuous to absent; when applicable, elevated above the mesoscutum in lateral view to not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate. The prosternal process interrupted, or entire; if not interrupted, complete. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities closed behind externally; broadly closed; medianly confluent, or narrowly 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 moderately to widely separated; not or scarcely oblique, or markedly oblique; closed laterally. Hind-leg coxae contiguous or narrowly separated, or widely separated; 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. Front tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented (depending on interpretation). Mid-leg tarsi 4-segmented, or 5-segmented; pseudotetramerous; 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, or one-toothed or bifid (sometimes toothed beneath); without an associated empodium. Hind tarsi with as many segments as the mid-tarsi; 4-segmented, or 5-segmented.

Elytral length/maximum width across the elytra 0.85–2.1. Elytra exposing no more than part of the terminal tergite to at least one but fewer than three complete abdominal tergites. 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, 10. Scutellary striole present (Anthribinae), or absent. Wings well developed, or absent or much reduced. Wings with an anal lobe (Urodontinae), or without an anal lobe (Anthribinae). Wings without a medial fleck. Abdominal sternites 5; comprising both fused and moveable components, or all fused and immoveable. Basal abdominal sternites immovably joined if not all connate, 3, or 4. Abdominal segment 8 apparently without functional spiracles. The male external genitalia chrysomeloid.

Adult habitat, ecology. Predacious (e.g., some Anthribus spp. being predators of coccoid Hemiptera), or not predacious; in decaying plant material, or in rotting wood, or on lichens, or associated with fungi, or in stored plant products (the cosmopolitan Araecerus coffeae being a notorious pest); consuming decaying plant material, or consuming rotting wood, or mycetophagous (the gut often containing fungal mycelium and spores).

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae elongate and more or less parallel-sided to oblong to ovate; C-shaped in lateral view. Body circular in cross-section to 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 1 segmented. Stemmata present, or absent; on either side of the larval head when present, 1. The frontoclypeal suture between frons and clypeus distinct. The labrum and head capsule separated by a complete suture. Apices of the mandibles with a single lobe or tooth, or bilobed or bidentate. The maxillary palps 2 segmented, or 3 segmented. The labium without ligula between the palps. Labial palps present and segmented; 1 segmented, or 2 segmented. Mesothoracic legs much reduced or absent; 1 segmented, or 2 segmented; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen entirely dorsal. The abdomen having functional spiracles on anterior segments (these annular, annular-uniforous or annular-biforous); 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 posterior segments without swimming hairs. The last abdominal segment without cerci.

Larvae not predacious; in rotting wood, in dried plant material, under bark, associated with fungi, and in stored plant products (associated with dead and dying trees, seeds and other plant products, and some with fungal rot or inhabiting ascomycete fruiting bodies); eating dried plant material or stored plant products, or consuming rotting wood, or mycetophagous.

Larvae curved, fleshy, widest in the middle, the head usually exserted and hypognathous, the antennae 1-segmented or absent; legs absent or very reduced.

Classification. Suborder Polyphaga; Superfamily Curculionoidea.

Representation in Britain and Ireland, and worldwide. Genera about 400. 8 species in Britain; genera in Britain 6; Anthribus, Platystomos, etc. E.g., Anthribus retinosus, Platystomos albinus.

General comments. Adults with the labrum free, membranous of separated by a suture; the procoxa with a long concealed, lateral extension, and the postcoxal projections solidly fused to one another (and sometimes to the poststernal process).

Illustrations. • Anthribus resinosus: B. Ent. 723. • Anthribus resinosus: B. Ent. 723, legend+text. • Anthribus resinosus: B. Ent. 723, text cont.. • Platystomos albinus: B. Ent. 726. • Platystomos albinus: B. Ent. 726, legend+text. • Platystomos albinus: B. Ent. 726, text cont.. • Anthribus resinosus, Brachytarsus (2 spp.), Choragus sheppardi, Platystomos albinus, Tropideres (2 spp., with Attelabidae and Nemonychidae): Fowler 5, 152 (1891). • Fowler 5, 152 (1891): original legend. • Anthribus resinosus, Platystomos albinus (Janson 232, 230). • Anthribus resinosus (Janson 232). • Brachytarsus “scabrosus” (= fasciatus? Rye & Fowler XI4).

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.’.