Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Pythidae

Excluding Mycteridae.

General appearance. 9–15 mm long. Body length/maximum body width 2.15–3.4. Elytral length/pronotal length 1.9–5.5. Base of prothorax distinctly narrower than the combined elytral bases. Greatest prothoracic width distinctly narrower than greatest elytral width. Body noticeably widest at the rear. Beetles elongate; dorsally flattened; not necked; conspicuously waisted; decidedly short-legged; elytra dark greenish to brownish, iridescent. Upper surfaces of body glabrous or subglabrous; not bristly; with neither scales nor scale-like setae.

Detailed morphology. Beetles without a rostrum; prognathous. Inclination of the head slight. Eyes strongly protuberant; without bristles; finely facetted. Ocelli absent. The frons without a transverse ridge between the eyes. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles with a reduced mola; with well developed prosthecae. The mandibular apices 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 somewhat expanded and truncate to subtriangular. The apical segment of the labial palps more or less expanded apically. Antennae short; 11 segmented; hairy. Antennal scape not swollen. Antennae filiform. Antennal insertions hidden from above; hidden by lateral extensions of the frons (under a shelf-like extension of the frons in front of eyes).

Cervical sclerites present. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.65–0.75. The pronotum without lateral keels. Prothorax at its widest markedly narrower than the adjoining part of the abdomen to not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Scutellum conspicuous; not elevated; anteriorly simple; posteriorly broadly rounded or obtusely angulate. The prosternal process present; incomplete; falling short of 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; medianly confluent; slightly transverse; without lateral extensions; internally open. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by less than the shortest diameter of the cavity. The mid-leg coxal cavities contiguous; not or scarcely oblique; open laterally. Hind-leg coxae contiguous or narrowly separated; not markedly extended laterally; 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 not appendaged. The claws of the mid-leg tarsi simple. Hind tarsi with one segment fewer than the mid-tarsi; 4-segmented.

Elytral length/maximum width across the elytra 1.7–1.9. Elytra exposing no more than part of the terminal tergite. The pygidium at least partly exposed beyond the long elytra. Elytra not truncate (but broad posteriorly and rather blunt); striate (with 9 or 10 rows). Elytra 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, 9, or 10. Scutellary striole absent. Elytra with epipleura to without epipleura. Elytral epipleura if present, falling short of the elytral tips. Wings without an anal lobe. Wings with a medial fleck, or without a medial fleck; the medial fleck when present, not bisected by a vein. Abdominal sternites 5; comprising both fused and moveable components. Abdominal segment 8 apparently without functional spiracles. The male external genitalia tenebrionoid.

Adult habitat, ecology. Not predacious (?); on living vegetation (Pytho depressus being associated with Scots pine).

Larvae. Mature larvae small to medium-sized to relatively large. The larvae elongate and more or less parallel-sided. Body circular in cross-section, or somewhat flattened, or strongly flattened (?). Vestiture restricted to fine hairs or setae. The larvae dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 3 segmented. Stemmata present; on either side of the larval head 5. 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, or with a ligula at least as long as 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, annular-biforous or annular-multiforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The last abdominal segment with cerci.

Larvae in rotting wood and under bark; consuming rotting wood (consuming decaying material under the bark of Pinus sylvestris).

Classification. Suborder Polyphaga; Infraorder Cucujiformia; Superfamily Tenebrionoidea.

Representation in Britain and Ireland, and worldwide. About 50 species worldwide. 1 species in Britain (P. depressus); genera in Britain 1; Pytho.

General comments. An elongate and parallel-sided, flattened, prognathous beetle, with each side of the thorax occupied by a deep depression; mesocoxal cavities contiguous at the middle; the mandible with reduced molar, and the incisor edge with two or more teeth.

Illustrations. • Pytho depressus, with Melandryidae and Salpingidae: Fowler 5, 147 (1891). • Fowler 5, 147 (1891): original legend..


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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