Pterostichus melanarius (Illiger, 1798)

Widespread and generally common throughout the Palaearctic region and now widespread across the United States, including Alaska, and Canada following introductions from Europe in the 1920s, this is among the most widespread and generally common members of the genus. In Europe it occurs from northern Spain to Italy and Greece in the south and extends north to the UK, Denmark and the Baltic countries where it reaches the Arctic Circle in Fennoscandia. Here it is common throughout England, Wales and Northern Ireland, and rather less so throughout Southern Ireland and Scotland north to Orkney.  The species occurs in a wide range of habitats from lowlands to alpine grassland, including grassland, open woodland, heaths, moorland, parks and gardens and may be particularly common on agricultural land, especially where cereals are grown. Adults occur year-round; they overwinter in soil or among tussock or under bark etc., and are active from March until late in the autumn, peaking in abundance during June and July. Reproduction occurs from June until September and both second and third-instar larvae remain active in all but the coldest winter periods. Eggs are laid in small groups in moist soil and many females will go on to overwinter and reproduce again during the following year, larvae develop through the winter and spring and pupation occurs in the soil from April. New generation adults appear over a long season during the summer, these will generally reproduce but those emerging late will usually overwinter before reproducing the following summer. Adults are mostly nocturnal and generally occur in numbers, they are almost exclusively terrestrial predators and are known to play an important role in controlling pest species in arable situations; prey include ants, mites, larvae, spiders, slugs and worms, and they are sometimes quoted as being able to consume more than their own body weight of prey daily. Most specimens in the UK lack wings or are brachypterous, but the species is otherwise wing-polymorphic; in Northern Europe fully-winged specimens tend to be uncommon but this varies regionally and in some areas they may exceed half the total number, this is thought to be of little importance with regard to dispersion as the species may walk 1.5Km or more each day, on the other hand the proportion of fully-winged individuals in North America tends to be high and this no doubt contributes to its rapid colonisation of forest biotopes in Canada. Adults may be sampled by searching at night or pitfall-trapping, but they are usually easy to find by turning debris on damp grassland etc.