There are over 2000 species in Europe, and almost 1000 species in Britain making this the largest beetle family in the U. K. They are commonly known as rove beetles. They range in size form less than 1 mm to 25 mm long.
The elytra (wing cases) are always short, and this gives the adults a superficial resemblance to earwigs. 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.
Staplinus olens (Ocypus olens), Devil's coach horse, cock-tail beetle
On the right is an adult Staplinus 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 Staphylindae 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. It is a matte black colour. Adults are common from May to September.