With a length of about 25mm, the Dark giant horsefly, Tabanus sudeticus, is reputed to be the heaviest fly in Europe.
Although the adult flies feed on nectar, it is only the females which will seek a blood meal - and then only after mating and before laying eggs. Unlike mosquitoes and midges which have a hypodermic needle-type mouthpart to pierce the skin, horseflies have serrated mandibles which tear the flesh, and the females lap the oozing blood. Fortunately, they usually feed on horses and cattle rather than humans!
The sexes can be differentiated by noting the presence or absence of a gap between the eyes: the eyes of male flies meet in the middle, whereas those of females are separated. The focus-stacked image indicates the specimen is a female fly.
