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.