This very widespread and generally common species occurs throughout Europe to the far north, and east through Asia to Japan; in the east it is represented by the subspecies czerskii  Zaitsev, 1953. It is widespread across the U.K. to the far north of Scotland, where it occurs above 500m, including the Western Isles but not Orkney or Shetland. They occur in most still or slow-moving aquatic habitats and are common or even abundant where found, they will colonize small water bodies e.g. garden ponds or even cattle troughs but generally prefer habitats on soft and silty or muddy substrates with plenty of vegetation although they seem to be less common in chalk or limestone areas. Adults occur year round; they spend the winter hibernating in the substrate at the bottom of ponds etc. and emerge early in the year, late winter or early spring depending on the season, and disperse by flying at night, at this time new environments are quickly colonized. Both the larvae and the adults are voracious predators, feeding on a wide range of aquatic life including newts and fish etc. and will also consume carrion, the young larvae are also cannibalistic at high densities. The adults will exude a foul smelling liquid from the abdomen when alarmed or threatened and this will generally deter predators. Eggs are laid in the spring when the females use the ovipositor to cut into the stems of aquatic plants and insert a single egg at a time, each female will work her way along a stem inserting eggs at short intervals so that, after a few days, there may be a sudden swarm of the small and transparent larvae. Despite being hidden in the plant stems the eggs are sometimes parasitized by tiny chalcoid wasps. Larvae begin hunting as soon as they emerge from the eggs, they obtain air by hanging upside down and protruding the abdomen through the water surface and because they are buoyant at this stage they spend much of their time thus suspended, snatching passing prey. Their large and curved mandibles are hollow and, after prey is caught, used to inject poisonous digestive juices which quickly disable it and then begin to liquefy the body contents, then after the contents have been sucked out the prey is discarded. They grow rapidly, increasing greatly with each moult, and the final instar is large  and heavy so at this stage they live  in shallow marginal