Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Mordellidae

Tumbling Flower-beetles, Pintail beetles.

General appearance. 2–9 mm long. Body length/maximum body width 2.3–4.7. Elytral length/pronotal length 2.2–3.75. 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; dorsally strongly convex (characteristically humped forward, and smoothly tapered to the uncovered tip of the abdomen); conspicuously necked; not waisted to somewhat waisted. Upper surfaces of body non-glabrous; not bristly; exhibiting scales or scale-like setae, or with neither scales nor scale-like setae.

Detailed morphology. Beetles not prognathous. Eyes not 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, or with a reduced mola. The mandibular apices simple. The incisor edges of the mandibles with a single tooth. The maxillae with distinct galea and lacinia apically to the palp. The apical segment of the maxillary palps somewhat expanded and truncate to subtriangular, or securiform to cultriform. The apical segment of the labial palps more or less expanded apically, or not expanded apically. Antennae short; 11 segmented. Antennal scape not swollen. Antennae filiform to gradually expanding towards the apex, or clubbed. Antennal clubs 7 segmented (elongate, serrate). Antennal insertions hidden from above.

Cervical sclerites present. Pronotal length/maximum pronotal width 0.45–1.1. The pronotum with lateral keels (pronotal carinae); keels complete. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or truncate, or emarginate. The prosternal process complete; falling short of the mesoventrite to 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; broadly open; narrowly separated; strongly transverse to slightly transverse; without lateral extensions; internally closed by a slender bar, or broadly closed internally. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by more than the shortest diameter of the cavity. The mid-leg coxal cavities moderately to widely separated; markedly oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; much enlarged; extending laterally to meet the elytra; not shaped posteriorly to receive the femur. Tarsal segmentation formula 5, 5, 4. The tarsi without bilobed segments; 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 with an appendage, or not appendaged; appendages when present, not or only lightly sclerotized. The claws of the mid-leg tarsi serrate, denticulate or pectinate (serrate or pectinate beneath, and each with a sclerotized process). Hind tarsi with one segment fewer than the mid-tarsi; 4-segmented.

Elytral length/maximum width across the elytra 1.55–2.53. Elytra meeting along the length of the mid-line; covering most to all of the abdomen; exposing at least one but fewer than three complete abdominal tergites (the exposed 1–2 tergites narrow-tapered to the exposed, long-pointed abdominal tip); non-glabrous. Elytra apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae. Scutellary striole absent. Wings well developed. Wings without an anal lobe. Wings without a medial fleck. The end of the abdomen extended as a long, narrow point beyond the ends of the truncate elytra. Abdominal sternites 5; all articulated and moveable. Abdominal segment 8 apparently without functional spiracles. The male external genitalia tenebrionoid, or not classified.

Adult habitat, ecology. On living vegetation and associated with flowers (and on tree trunks); phytophagous (e.g., feeding on pollen).

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae elongate and more or less parallel-sided. 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 1–3 segmented. Stemmata present, or absent; on either side of the larval head when present, 1–3. 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. The maxillary palps 2 segmented, or 3 segmented. The labium without ligula between the palps, or with a short ligula between the palps. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented; 3 segmented, or 4 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); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci, or without cerci.

Larvae predacious (or parasitic, according to Britton, 1970), or not predacious (?); in living vegetation, or in rotting wood, or associated with fungi (e.g., in polypore fruit bodies); if not predatory, phytophagous (leaf- or stem-mining recorded in Mordellistena).

Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Tenebrionoidea.

Representation in Britain and Ireland, and worldwide. About 1500 species worldwide. 10 species in Britain; genera in Britain 3; Mordella, Mordellistena, Tomoxia. E.g., Mordellistena abdominalis (Red-bodied Mordella).

General comments. Small to medium sized beetles with deflexed heads, characteristically humped and smoothly tapered behind to a long, stout spine. Protectively tumbling in series of rapid jumps when alarmed.

Illustrations. • Mordellistena abdominalis (Red-bodied Mordella: B. Ent. 483). • Mordellistena abdominalis (details, B. Ent. 483). • Mordellistena abdominalis: B. Ent. 483, legend+text. • Mordellistena abdominalis: B. Ent. 483, text cont..


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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. delta-intkey.com’.

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