Wikipedia
The family Strashilidae is an extinct group of Jurassic flies from Siberia and China. They were originally believed to represent a distinct order called Nakridletia, but recent research has determined that they were flies related to the extant family Nymphomyiidae, and two of the species (and genera) in the group were determined to be synonyms. The original hypothesis was that the insects were wingless and were probably ectoparasites of pterosaurs, mostly due to their enlarged hind legs, which were theorised as useful for grasping hair and feathers; however, additional fossils showed that both sexes had deciduous wings, and that only males had enlarged hind legs, used to grasp the females during mating. The family is now known from two species in the genus Strashila and one in the genus Vosila.