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Devil's Coach-horse an aggressive little beetle beast

If it feels under threat, the Devil’s Coach-horse rears up its head and open sits jaws wide and curls up its tail like a scorpion

Jim Hurley - Nature Trail
© Bray People

The Devil's Coach-horse is a common black beetle that will be familiar to many people as it has a habit of sometimes wandering indoors. It is an aggressive little beast that readily puts on a threat display when confronted by a person very many times its size.

It has a long body and very short wing cases making it look a bit like a black earwig. Unlike the Common Earwig, the Devil's Coach Horse doesn't have pincers on its tail end. It does, however, have large pincer-like jaws at its front end and these can inflict a painful bite.

If it feels under threat it rears up its head and opens its jaws wide and curls up its tail like a scorpion. It also emits a foul smell from glands on its abdomen. This scary threat display, the powerful jaws, the threat of a bite, the scorpion-like tail, the bad smell and the black colour all combine to give this beetle a long-standing evil connotation. Since medieval times the beetle has been associated with the devil, curses and superstition.

Out of doors, in gardens, hedgerows, parks and woodlands, the Devil's Coach Horse is nocturnal. By day it rests under stones, logs and in leaf litter. As night falls it emerges to hunt. While it has small wing cases it seldom flies. It hunts on foot and can tackle large prey like an adult earthworm or a big slug. Its large, pincer-like jaws are formidable weapons for catching and processing food.

The Devil's Coach Horse is a member of the rove beetle family, a very large group of insects characterised by their short wing cases and habit of being constantly on the move, rambling and roving and wandering. It is their roving habit that results in them sometimes entering people's homes. The Devil's Coach Horse has the distinction of being both the largest member of the family found in Ireland and one of the more common species likely to be encountered by most people.

Adults breed in autumn. If the winter weather is particularly harsh early on many adults die and it is the young that overwinter in the soil emerging as adults when spring arrives around March. If the winter is not particularly harsh some adults survive into their second year.

If conditions are unseasonably mild many will make into the following year to continue their rambling and roving and putting on the threat display that has given them their bad name.