Identification - The hornet robberfly is a very large and distinct predatory fly (Diptera - true flies) and is one of the biggest in Britain. They are very bristly, have sturdy legs, a deep groove between the eye and a 'beard' to protect the eyes. (Chinery 1986) It is a nationally notable species that is much declined in south-eastern England, and is currently only known in Essex from several cattle or horse grazed sites near the Thames.
General ecology - It is found in unimproved or old grassland and heath, with a long continuity of grazing. The fly breeds on cow pats and other dung and the larvae (maggots) are thought to feed on dung beetle larvae. The adults are found from late July to early October and catch a variety of insects in mid-air and suck them dry. They are usually found resting on cow or horse pats and when disturbed they tend to fly a short distance to a nearby pat.
Surveying tips - Please send in any records using the survey card.
Photo copyright Peter Harvey