There are around 27,000 species worldwide, over 5000 species of Staphylinids in Europe, and around 900 species in the British Isles making this the largest beetle family in the U. K. They are commonly known as rove beetles. They range in size from less than 1 mm to around 30 mm long.
The elytra (wing cases) are always short, and this gives the adults a superficial resemblance to earwigs. They are also sometimes confused with beetles from the Silphidae family. However it is really quite easy to tell the two families apart. Silphids have just 3 or 4 exposed segments, and the wing cases are longer than these exposed segments; whereas the Staphs have 3 to 6 exposed segments, and the wing cases are always shorter than the exposed segments.The elytra cover intricately folded wings, and in most species flight is common. It is amusing to watch one just after it has landed, it will wriggle around while its wings are being folded up under the elytra, and only once they are correctly packed away will the beetle move off.
Most of the adults have conspicuous cerci at their rear end. These act just like antennae, and are highly sensitive and useful for a soil-dwelling insect.
Creophilius maxillosus, the Hairy rove beetle, above is black with patches of white/yellowish/grey hairs on its elytra (wing cases) and abdomen. Adults range from 15 - 25 mm long. It is found across the northern hemisphere in temperate regions.
Both the adults and larvae are carnivorous It feeds on carrion, and the maggots in carrion. It has large eyes, and strong jaws which cross in front (see below) which could easily pierce human skin if mishandled. When it is disturbed it curls up its abdomen and emits a mix of an irritant chemical from glands located on the underside of the tip of its abdomen and faecal matter, smearing it on whatever has disturbed it. It will also curl up into a ball and play dead.
Above is an adult Staphylinus olens (Ocypus olens), commonly known as the Devil's coach horse or the cock-tail beetle. At up to 30 mm long it is the largest member of the Staphylinidae family found in the U. K.
When alarmed it opens its large jaws and curls up its abdomen rather like a scorpion. Its jaws are strong enough to draw blood from humans. It is a matte black colour. Adults are common from May to September.
Above and below is the adult Ontholestes tessellatus. The adult length ranges from 13 - 20 mm. It is usually found in carrion and dung, but this one was found on the top of a soggy compost heap.
It is truly beautiful, covered in golden hair which has brassy reflections as it moves. Its eyes are huge and its jaws are fearsome. It runs very fast and is not easy to catch.
Below is the larva of Philonthus sp. showing the typical staphylinid larval body shape.