Oodes helopioides (Fabricius, 1792)
This western Palaearctic species is widespread in Europe from Spain to the south of Fennoscandia, reaching Italy and Greece to the south and extending east through Russia to Western Siberia; it is generally common in northern areas but much more local and rare in the south e.g. it is Red-Listed in Switzerland and rare in Southern Germany. Here it is widespread though very local across southern England and South Wales and more scattered and rare further north to Cumbria; with the exception of the West Country most records are below a line from the Severn estuary to the Wash and hotspots include the south coast from Kent to Dorset, the New Forest and parts of East Anglia. This is primarily a lowland species, occurring up to about 800m in Europe, which is restricted to a range of well vegetated wetland habitats, typically the shaded margins of still or slow-moving water on muddy or silty soils but also in peat bogs and marshes, especially where there are areas of dense grass such as Carex or Glycera, or reeds, or where shade is provided by willow or alder. Adults are fully winged but probably fly only when their habitat is drying out; otherwise they occasionally move far from wetlands and so might be sampled in apparently unusual situations. They are adapted to a partially aquatic way of life; they crawl up and down grass and reed stems and move underwater with ease, sometimes apparently swimming, and when disturbed will enter the water and remain submerged for some time, both adults and larvae are predatory and both are known to cannibalistic. Adults are diurnal and nocturnal, they occur year-round although they may be absent for a while in the summer; mating occurs in spring and summer and larvae develop during June and July to produce new-generation adults in late summer. These adults will overwinter among litter or in tussocks close to the water edge and become active from the following April.
Oodes helopioides 1
Oodes helopioides 2
Medium sized, 7.5-10.0mm, entirely black and almost continuous in outline, this species is suggestive of a large Amara but may be distinguished by the single setiferous puncture beside each eye and the lack of setae on the palps. The upper surface is rather dull due to fine microsculpture and very fine punctures. Head smoothly convex, with convex and prominent eyes and long slender antennae and palps; the third antennomere is glabrous and the penultimate maxillary palpomere about twice as long as the terminal segment. Pronotum transverse and widest about the middle, strongly narrowed to rounded anterior angles and much less strongly narrowed to perpendicular posterior angles, basal margin bisinuate, and the surface is usually wrinkled towards the base but without fovea. Elytra parallel-sided and continuously rounded apically, each with eight finely-punctured striae and a scutellary striole, the eighth slightly raised and forming a sub-lateral keel around the apical margin. Interstices flat or only very weakly convex, the third with two setiferous punctures in the apical half; these are close to the second striae but do not connect. Male with dilated basal pro-tarsal segments.