The Terrible hairy fly (Mormotomyia hirsuta Austen)

Mohamed bin Zayed Species project number 11252410

 

In 1936, Austen described a strange, hairy and brachypterous fly from two male specimens collected at Ukasi (as Ukazzi) in 1933 by Major Harry Barron Sharpe, then District Commissioner of the large Garissa District of eastern Kenya. The fly was characterized by its presumed association with bat guano, its greatly reduced and dysfunctional strap-like wings, the reduced eyes and absence of ocelli, its numerous long hair-like setae (especially on males), and by its superficially spider-like appearance. Austen named the species Mormotomyia hirsuta, the “frightful hairy fly”, now known popularly as the “terrible hairy fly”.  Until 1948, these two specimens remained the only known examples of this extraordinary species. In December of 1948, following heavy rainfall, the species was again collected, this time in large numbers by the noted Kenyan naturalist Victor Gurner Logan van Someren. This collection, that included numerous specimens of adult females, larvae and puparia, was made at the type locality (Ukasi), apparently from the same large, split boulder at which Sharpe collected the original series. In the 62 years since the species was last collected, numerous efforts to relocate it at the type locality have been unsuccessful.

Mormotomyia hirsuta remains a species of considerable interest. The adult fly is truly bizarre-looking, and its vernacular name only slightly exaggerates its appearance. The only representative of the dipterous family Mormotomyiidae (confined to the Afrotropical Region), M. hirsuta is currently considered the rarest fly in the world, and is known only from the type locality. Of particular interest is whether the relationship of M. hirsuta with bats extends beyond larval nutrition alone, to adult phoresy (dispersal of the flies on flying bats). It is also not known whether other populations exist in similar habitats, or whether Ukasi Hill represents the only relict site. Finally, in light of the contradictory evidence presented by morphological character states of both the larval and adult stages, its systematic position within the order Diptera remains uncertain. Not surprisingly, diverse opinions regarding the phylogenetic position of Mormotomyia have appeared in the literature. Advances in molecular phylogeny hold promise that the phylogenetic position of Mormotomyiidae within the Diptera could be resolved; a promise, however, that awaited freshly-collected specimens.

In November–December 2010, an expedition was undertaken to search for the fly, timed to coincide with Kenya’s short rainy season; the period during which van Someren found flies in abundance. Good fortune allowed us to rediscover Mormotomyia and to make preliminary observations on its biology and behavior. We were also able to supply fresh specimens to molecular geneticists to use in phylogenetic studies and to assess the amount of genetic diversity in the population. Our project funded by the Mohamed bin Zayed Species Conservation Fund focuses on exploration for other potential populations of Mormotomyia and studies of the behavior of this remarkable species.