This is one of the most widespread and common Palaearctic members of the genus; it occurs in North Africa and throughout Europe to the far north of Scandinavia and extends east through Asia Minor and Siberia to the eastern shores of Russia. It is generally distributed throughout the UK, including all the islands north to Shetland, and is locally common although in our experience adults are rarely found in numbers. Adults are present year-round; they are active from early in the year until October or November depending on the season and peak in late spring or early summer, they inhabit a wide variety of still and slow-moving water; typically small ponds and lake margins but also reed beds, moorland pools and canals etc. and we have sampled them from a cattle-trough on a local common, they are tolerant of a wide range of conditions from densely-vegetated ponds in wooded areas to lake margins devoid of vegetation. Adults occur year-round and mating pairs have been recorded in both spring and autumn although breeding typically occurs in the spring; females lay eggs above the water among vegetation or debris and larvae emerge after a week or so. The larvae are predaceous and actively hunt a range of small prey; under artificial conditions they have been shown to be very effective predators of mosquito larvae and have been considered for use as bio-control agents, they digest prey by injecting them with enzymes and then sucking out the contents whereas adults consume prey directly. They develop rapidly and are fully-grown after about a month at which time they leave the water to pupate in a cell among marginal substrate or debris. Adults eclose between two weeks and a month following pupation and return to the water for the summer but they are good fliers and move readily between water bodies, occasionally appearing at light traps or in temporary ponds etc, they remain active until late in the year when they move to permanent aquatic habitats in which to overwinter. They are active and hunt both by day and by night, during the day they evade predation by swimming but by night they use poisonous and very effective defence fluids to deter predators.  Sampling is usually straightforward using the basic methods of sweeping along the margins of ponds or leaving out baited bottle-trapping but adults can swim very quickly and are adept at avoiding threats and so vigorous sweeping might be needed.