National History Museum

World’s rarest fly rediscovered

Mormotomyia hirsuta Female

On a recent trip to Kenya, Ashley Kirk-Spriggs, Entomologist at the National Museum, and Bob Copeland (International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, were fortunate to re-discover the bizarre wingless fly, Terrible Hairy Fly (Mormotomyia hirsuta), which has only been collected twice before, in 1933 and 1948, although several expeditions have subsequently been unsuccessful in re-discovering the species.

The fly belongs to a family of its own, the Mormotomyiidae, which is endemic to the Afrotropical Region.  The systematic position of this family within the higher flies has long been an anomaly and we now have suitably preserved specimens (collected during our trip) for molecular analysis. The situation regarding its systematic position can now at last be resolved.

Mormotomyia hirsuta Male
Mormotomyia hirsuta Male

The species is known from only a single locality in the world and is the world's 'rarest fly'.  The flies are associated with bats and the larvae develop in the bat guano following heavy rains when this is washed from a cleft in the rock inhabited by the bats.

The flies have the forewings reduced to tiny straps, and have enormously long legs, clothed in immensely long hairs which they use as a parachute to drift down from the roof of the rock crevice in which they live.

This discovery represents a major leap forward in our understanding of the systematics of the higher flies and is causing a great deal of excitement within the dipterological community worldwide.

Top photo:Mormotomyia hirsuta Female