Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz


Including Thorictidae, Thylodriidae, Thylodriadidae.

Museum, Carpet, Skin, Hide, Larder, Leather (etc.) Beetles.

General appearance. 1.5–8 mm long. Body length/maximum body width 1.42–3. Elytral length/pronotal length 1.72–5.33. 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 oval to elongate (generally robust); having ventral body cavities into which the legs fold to conform with the general body surface, or without ventral body cavities for reception of the legs (?); not necked; not waisted to somewhat waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; exhibiting stiff, erect, dark bristles, or not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae.

Detailed morphology. Inclination of the head slight to very strong. Eyes strongly protuberant, or not strongly protuberant; bristly, or without bristles. Ocelli present, or absent; when present, solitary (median). The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a reduced mola (Thylodiinae), or without a mola (mostly). The mandibular apices simple, or bidentate or bilobed. The incisor edges of the mandibles simple (often), or with a single tooth. 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; 9 segmented, or 11 segmented. Antennal scape not swollen. Antennae clubbed. Antennal clubs 3–5 segmented; preceded by a cupule, or without a cupule. Antennal insertions visible from above.

Cervical sclerites present. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.37–1. The pronotum with lateral keels (pronotal carinae) (except in anelytrous females of Thylodriinae); keels complete, or incomplete. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Hind corners of the thorax not extended rearwards into sharp points. Scutellum conspicuous to highly reduced, or absent (Thorictinae); when applicable, elevated above the mesoscutum in lateral view (usually), or not elevated (rarely); anteriorly where known, simple; posteriorly narrowly rounded or acute (usually), or truncate. The prosternal process present, or absent; when present, variously complete, or incomplete; when present, variously falling short of the mesoventrite to moderately or strongly overlapping the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’, or attached externally, in the absence of procoxal cavities (only in Thylodrias). The fore-leg coxal cavities usually open behind externally; broadly open; varously medianly confluent, or narrowly separated, or quite widely separated; strongly transverse, or slightly transverse, or circular to longer than wide (Thorictinae); with narrow lateral extensions, or without lateral extensions; internally open, or internally closed by a slender bar, or broadly closed internally. The mid-leg coxae countersunk in ‘mesocoxal cavities’ (mostly), or attached externally, in the absence of mesocoxal cavities (both males and females of Thylodriinae); separated by when countersunk, less than the shortest diameter of the cavity, or more than the shortest diameter of the cavity. The mid-leg coxal cavities narrowly separated, or moderately to widely separated; not or scarcely oblique; when present, open laterally. Hind-leg coxae contiguous or narrowly separated, or widely separated; not markedly extended laterally (mostly), or extending laterally to meet the elytra (some Trinodinae). Tarsal segmentation formula 5, 5, 5, or 5, 5, 4. The tarsi without bilobed segments; with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth (hind tarsi, sometimes), or with a tiny basal segment that is hard to detect, or without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous; 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. Hind tarsi with as many segments as the mid-tarsi; 5-segmented.

Elytra present (except in the larviform females of Thylodrias contractus, which may be encountered as an introduction). Elytral length/maximum width across the elytra 1–2.35. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite, or at least three complete abdominal tergites; not truncate; non-glabrous (often covered with fine hair or scales), or glabrous. Elytra apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae. Scutellary striole absent. Wings well developed, or absent or much reduced (in females and some males of Thylodriinae). Wings variously with an anal lobe, or without an anal lobe. Wings without a medial fleck. Abdominal sternites 5; all articulated and moveable, or comprising both fused and moveable components. Basal abdominal sternites immovably joined when present, 2. Abdominal segment 8 with apparently functional spiracles. The male external genitalia bostrichoid.

Adult habitat, ecology. Land-dwellers; not predacious; variously on living vegetation, or in decaying plant material, or in rotting wood, or in dried plant material, or on shed fur or feathers, or associated with flowers, or in stored plant products; feeding on dried animal remains, or consuming decaying plant material, or eating dried plant material or stored plant products, or consuming rotting wood.

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae elongate and more or less parallel-sided, or oblong to ovate. Body somewhat flattened. Vestiture restricted to fine hairs or setae (Orphilinae), or not restricted to fine hairs or setae. The larvae dorsally heavily pigmented or sclerotized, or dorsally only very lightly pigmented or sclerotized (Thorictinae only); ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present, or absent (commonly); on either side of the larval head when present, 3–6. The frontoclypeal suture between frons and clypeus indistinct or absent, or 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, or trilobed or tridentate. The maxillary palps 3 segmented, or 4 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, or extending to the underside, or completely ventral. The abdomen having functional spiracles on anterior segments (these annular); without spiracular tubes. Abdominal tergum 8 without amature. The last abdominal segment with cerci, or without cerci.

Larvae not predacious; in dried plant material, in carrion, and in shed fur or feathers, or in stored plant products; feeding on dried animal remains, or eating dried plant material or stored plant products (on material of high protein content, mostly of animal origin - carcasses, insect remains, skins, bacon, etc., but some Trogoderma species feed on dry plant materials).

The scarabaeiform larvae subcylindrical, elongate- to short-oval and clothed with long setae, six well developed legs, antennae 3-segmented, 3 to 6 lateral ocelli.

Classification. Suborder Polyphaga; Superfamily Dermestoidea.

Representation in Britain and Ireland, and worldwide. 500–700 species worldwide. 30 species in Britain; genera in Britain 9; Anthrenocerus, Anthrenus, Attagenus, Ctesias, Dermestes, Globicornis, Thylodrias, Trinodes, Trogoderma. E.g., Ctesias serra (Toothed-horn Megatoma); Dermestes lardarius.

General comments. Males and females of Thylodrias contractus - an occasional introduction - lack procoxal cavities, so that the procoxae are attached externally.

Illustrations. • Attagenus trifasciatus (Adventive: B. Ent. 247). • Attagenus trifasciatus: B. Ent. 247, legend+text. • Attagenus trifasciatus: B. Ent. 247, text cont.. • Ctesias serra (Toothed-horn Megatoma: B. Ent. 244). • Ctesias serra: B. Ent. 244, legend+text. • Ctesias serra: B. Ent. 244, text cont.. • Dermestes lardarius: B. Ent. 682. • Dermestes lardarius: B. Ent. 682, legend+text. • Dermestes lardarius: B. Ent. 682, text cont.. • Anthrenus, Ctesias, Megatoma, Trinodes (with Byrrhidae, etc.): Fowler 3, 97 (1889). • Fowler 3, 97 (1889): original legend.. • Attagenus pellio, A. trifasciatus and Dermestes (3 spp.), with Mycetophagidae: Fowler 3, 96 (1889). • Fowler 3, 96 (1889): original legend.. • Globicornis nigripes (with Cryptophagidae, Dryopidae, etc.): Fowler Suppl. 14, 1913. • Fowler 6, 14 (1913): original legend.. • Dermestes lardarius (Janson 177).

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.’.