Scientists in Kenya have located one of the world's rarest and oddest-looking flies after a long hunt for an insect dubbed the ''terrible hairy fly'', experts said on Wednesday.

Scientists first stumbled across the yellow-haired fly in 1933 and then again in 1948. Since then, at least half a dozen expeditions have visited a site between the towns of Thika and Garissa to find it again.

At about one centimetre long and so far found on a single 20-metre high rock, the Mormotomyia hirsuta looks more like a spider with its hairy legs, scientists said.

Unable to fly and partial to breeding in bat faeces, the fly is thought to live only in the dank, bat-filled cleft of an isolated rock in the Ukazi Hills. It also has non-functional wings that resemble miniature belt-straps, and tiny eyes.

Dr Robert Copeland of the Nairobi-based International Centre of Insect Physiology and Ecology said the fly's physical appearance had left scientists bamboozled about where exactly it belonged in the entire order of Diptera, or ''true flies''.

''We have collected fresh specimens for molecular analysis to see where exactly the 'terrible hairy fly' fits into the evolutionary process,'' Copeland told Reuters by telephone.

''The fly has no obvious adaptations for clinging onto other animals for transfer from one place to another. With its long legs, it could perhaps wrap itself around a bat and get a ride ... but it's never been found elsewhere.''

The Mormotomyia hirsuta is the only member of its biological family and some fly experts reckon the fly will eventually prove to be the only family of fly completely restricted to Africa.