Philonthus decorus (Gravenhorst, 1802)

This is a widespread and generally common species throughout England and Wales, with the probable exception of the West Country but including Anglesey and Man, and though more local and scarce further north extending to the far north of Scotland and Orkney. It is widespread across central Europe though sporadic; generally more common in northern and mountainous areas though rare in e.g. Poland, extending north into Fennoscandia, south to the Pyrenees, Italy and the Balkans and east to (at least) western parts of Siberia. Typical habitats are damp woodland and densely vegetated marginal areas, in upland situations often under rocks or among stones beside streams and bogs and on the continent among sphagnum bogs etc. in mountain areas. Adults occur year-round and are generally active from March to October with peaks in May and September, they overwinter under logs or among moss or leaf-litter and may become active during mild spells; they are nocturnally active on the ground and may be seen by torchlight as they move rapidly hunting for snails, slugs and small insects. During the summer they may occur in numbers under large logs and where several of these lie close together each may all harbour a small group of specimens, adults will almost always be found in damp and shaded habitats throughout the year and only rarely venture out onto pathways or open ground during the warmer months. Mating occurs mostly during the spring population peak around May and oviposition begins soon afterwards; eggs are laid singly in the soil and each female will lay around 20, this may continue into July although by this time very few are still laying, and at least some of this population will go on to overwinter and oviposit for a second time. Larvae develop through the summer and pass through 3 instars before pupating during September; they are generally predaceous and at this time have been recorded consuming eggs and larvae of winter moths, along with various other staphs and carabids, and may become a controlling factor when moth populations are large. New generation adults appear from September, producing a second population peak, and will feed until the winter when they become inactive. Adults will soon be recognized in the field; the large size, metallic colouration and contrasting shiny forebody and matt elytra are distinctive.