Ocypus olens (Muller, O.F., 1764)

Author - Conall Murray (Junior member)

A common and often very abundant species throughout Great Britain and Ireland. ¹ They are found in just about every habitat, including out buildings with the exception of, in our experience, very moist habitats, e.g. waterside. They are very abundant on parkland pathways and some urban pavements nocturnally throughout the Watford area between July and September, during this time they are active, running fast and sometimes observed feeding on the crushed remains of carabids and slugs. They increase in abundance through the summer reaching their peak in late August/early September when large carabids are absent due to summer aestivation before abruptly disappearing, no doubt due to the decrease in nocturnal temperatures, in late September/early October. At their most common, they can be found occupying pathways rarely more than 15ft apart. We have only recorded one specimen in flight. Throughout the year they may be found in woodland, during the day active amongst leaf litter, but generally under logs often in pairs or sometimes in small groups. During the winter almost always under logs and sometimes in company with larger carabids e.g. Pterostichus spp. or Cychrus. As well as feeding on smaller invertebrates they are known to feed on carrion. ² When disturbed the beetles assume a defensive posture, raising the abdomen and head while opening their mandibles wide; when handled they may bite and are apparently capable of drawing blood.

The largest european staphylinid which cannot be confused with any other British species even in the field.
20-28mm. Broad and more or less parallel, completely black except for terminal antennal segments which are dull orange. Entire upper surface is dull and finely punctured wih short, dense, black or rarely red, pubescence. Side of head, thorax, elytra and abdomen with long outstanding setae. Head transverse, wider than thorax. Smooth, without sculpture and with large, sharp mandibles. Eyes small, temples long with rounded hind angles. Antennae longer than head, not, or only just, thickened towards apex, inserted within outer margin of mandibles, insertions placed further apart than joint 1. Thorax slightly elongate, without sculpturation or smooth areas and very finely bordered. Elytra slightly transverse, without sculpture or depressions. Suture simple. Scutellum punctured and dull as elytra. Abdomen parallel sided with strongly raised borders, slightly shining in contrast to the front parts. Legs long and robust, tibia strongly spinose, front tarsal segments strongly dilated.

¹ Complete British Insects, Chinnery, M. Collins 2005
² Bugs and Insects magazine Vol. 10 2007.

Description from 2 Watford specimens at X10