British insects: the families of Coleoptera
British insects: the families of Coleoptera |
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Minute Marsh-roving Beetles.
General appearance. 1.5–1.8 mm long. Body length/maximum body width 1.3–2.15. Elytral length/pronotal length 2.4–4.7. 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, or distinctly narrower than greatest elytral width. Beetles oval; dorsally strongly convex; having ventral body cavities into which the legs fold to conform with the general body surface; not necked; not waisted. Upper surfaces of body glabrous or subglabrous, or non-glabrous; not bristly; with neither scales nor scale-like setae.
Detailed morphology. Inclination of the head slight to very strong. Eyes strongly protuberant, or not strongly protuberant; without bristles. Antennae short; 7 segmented, or 11 segmented; weakly clubbed. Antennal clubs 1 segmented. Antennal insertions visible from above, or hidden from above. Mandibular prosthecae well developed. Pronotal length/maximum pronotal width 0.3–0.65. Prothorax without notopleural sutures. The scutellum elevated. Metaventrite with a transverse groove, or without a transverse groove. Hind coxae posteriorly shaped to receive the retracted femur; with a steep transverse declivity against which the femur retracts. Tarsal segmentation formula 5, 5, 5. 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 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. Elytral length/maximum width across the elytra 1–1.65. Elytra exposing no more than part of the terminal tergite. Scutellary striole absent. Wings well developed, or absent or much reduced. Exposed abdominal sternites 5; comprising both fused and movable components, or all fused and immovable; immovably joined 3, or 5. Abdominal segment 8 with apparently functional spiracles.
Adult habitat, ecology. Land-dwellers (but living on the margins of water courses).
Larvae. Larvae aquatic.
Classification. Suborder Polyphaga; Infraorder Elateriformia; Superfamily Dryopoidea.
Worldwide and British representation. About 270 species worldwide; genera about 35. 1 species in Britain (L. pygmaeus); genera in Britain 1; Limnichus.
General comments. The tarsi in non-British species sometimes pseudopentamerous or tetramerous, sometimes also with lobed segments. The beetles’ ventral surface exhibits cavities into which the legs can be folded.
Illustrations. • Limnichus pygmaeus (from Joy). Limnichus pygmaeus (Limnichidae). Eubria palustris (Psephenidae). • Limnichus pygmaeus (with Dermestidae, Byrrhidae, etc.): Fowler 3, 97 (1889). • Fowler 3, 97 (1889): 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. British insects: the families of Coleoptera. Version: 2nd January 2012. http://delta-intkey.com’.
