Devil’s coach horse beetle

The devil’s coach-horse beetle (Staphylinus olens) is a very common and widespread European beetle belonging to the large family of the Rove beetles (Staphylinidae). It is also called Ocypus olens by some authors. This species has also been introduced to the United States, New Zealand and Australia.

This black beetle shelters during the day under stones, logs or leaf litter, and is most often found in forests, parks and gardens between April and October. It is a long-bodied beetle measuring in at about 25-28mm and is one of the larger British beetles. Its wing covers (elytra) are short, covering only its thorax, exposing the abdominal segments. The abdominal musculature is powerful and the abdominal segments are covered with sclerotized plates. Even though it is capable of flight, its wings are rarely used. It is also covered with fine black hairs over its entire body.

It is well known for its habit of raising its long and uncovered abdomen and opening its jaws, rather like a scorpion when threatened. This explains one of its alternative names, the cock-tail beetle. Although it has no sting it can give a painful bite with its strong pincer-like jaws. It also emits a foul smelling odor, as a defensive secretion, from a pair of white glands at the end of its abdomen. In the scientific name olens means oily and describes this secretion.

This predatory beetle hunts mainly by night, feeding on invertebrates including worms and woodlice, as well as carrion. Prey is trapped between the mandibles which are also used to cut and together with the front legs to manipulate the food into a bolus. The bolus is repeatedly chewed and swallowed, emerging covered with a brown secretion from the foregut, until it is reduced to a liquid which is digested. Skin (in the case of earth worms) and hard materials (from arthropods) are left. The larvae are also carnivorous with similar eating habits.

Females lay their eggs two to three weeks after mating. These large (4mm) eggs are white with a darker band and are laid singly in damp conditions under moss, stones, cow pats or leaf litter, typically in the Autumn. Incubation lasts about 30 days, after which the eggs split and the larvae emerge. The larva lives largely underground using its well-developed mandibles to feed on similar prey to the adult beetle. It adopts the same display with open jaws and raised tail when threatened.

The larva goes through three stages of growth. The final stage ranges from 20 to 26mm in length. At around 150 days the larva pupates for about 35 days and emerges as an adult with its final coloring, fully formed except for the wings which cannot be folded neatly beneath the elytra for several hours. Adults can survive a second winter, some by hibernating in burrows and not emerging until March while others remain active.

This beetle has been associated with the Devil since the Middle Ages, hence its common name. Other names include Devil’s footman or Devil’s steed. In Ireland the beetle is known as darbhadal (literally Devil’s beast) and it is said that the Devil assumes the form of this beetle to eat sinners. As with many supposed bringers of ill-luck superstition holds that people can turn the creature’s powers to their own advantage and it is said that reapers used to enclose the body of a Devil’s coach horse beetle in the handle of their scythes to improve their skill. The origin of these beliefs can perhaps be explained by the beetle’s threatening appearance, and its habit of eating carrion.