Cymbiodyta marginella (Fabricius, 1792)
POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
HYDROPHILINAE Latreille, 1802
Cymbiodyta Bedel, 1881
This Palaearctic-wide species is generally distributed from Portugal and Asia Minor to the far east of Russia, it occurs mostly in lowlands but there are scattered records from montane regions where it can be abundant in raised bogs. In Europe it extends from the Mediterranean, including many of the islands but not in North Africa, north to the UK and the Baltic countries where it reaches southern provinces of Norway and Sweden with occasional records further north. It is locally common throughout most of this range, although it seems to less so and probably declining in the south. In the UK it is generally common across England including all the islands, though much less so in the West Country and across the North-East, it is mostly coastal in Wales, and is widespread though very local in Ireland. Typical habitats are margins of well-vegetated drains, marshes, pools and lakes, sometimes in grassy pools on heaths and moors, and usually in calcareous or base-rich areas, but it can be common in peatland e g on the Somerset Levels, and specimens occasionally occur in brackish pools in coastal areas. Adults occur year-round and peak in abundance during April or May. They generally overwinter among matted vegetation or under debris out of water, and they have been recorded in numbers from debris of old avian nests, they are easily found at this time by sieving likely material, and they sometimes occur in numbers among flood refuse. From early spring they may be found in numbers among both aquatic and terrestrial vegetation in shallow marginal situations. They disperse by flight on warm spring days or summer evenings, and specimens sometimes occur in light traps. The biology is unknown, but typical of the group larvae are thought to be predaceous while adults are vegetarian or detritivores.
Cymbiodyta marginella 1
Cymbiodyta marginella 2
3.3-4.3 mm. Elongate-oval, dorsal surface shiny, glabrous and convex, ventral surface densely pubescent and flat, body shiny black, usually with the pronotal and elytral margins at least partly pale, palps brown, antennae pale with darker clubs, legs black with brown tarsi. Head transversely impressed across the frons, otherwise smoothly convex and finely and densely punctured throughout, eyes large and continuous with the outline, temples short and converging, clypeal margin smoothly rounded. Maxillary palpi much longer than the antennae; terminal segment shorter than the penultimate segment. Antennae 9-segmented; segment six forming a short and transverse pedicel before a loose 3-segmented club. Pronotum transverse, broadest across rounded (from above) posterior angles and narrowed to slightly projecting anterior angles and a curved apical margin, basal margin curved and at most only very finely bordered laterally. Pronotal surface evenly convex and finely and densely punctured throughout. Scutellum triangular and punctured as the adjacent pronotal surface. Elytra elongate, smoothly convex and evenly-curved from rounded shoulders to a continuous apical margin, sutural striae well-impressed from the basal third or half, surface otherwise finely and densely punctured, without striae although there are often several longitudinal rows of slightly larger punctures. Femora narrow and with paired apical spurs. Tarsi 5-4-4, without lobed segments. Claws smooth and without a basal tooth.