What is the rarest type of fly?

What is the rarest type of fly? The rarest type of fly is difficult to define as many rare species exist, but among known rare flies are those that are highly specialized or endangered. Examples include the New Zealand bat fly Mystacinobia zelandica which lives only on New Zealand lesser short-tailed bat and is rare due to host rarity. Another rare fly is the flightless fly Badisis ambulans from Australia that is wingless and lives in pitcher plants. The giant blue bottle fly? Among more known, the teratomyzid flies are rare family. The rarest may be species with very limited range like the Hawaiian Drosophila species that are endangered and live only on single islands. Some bot flies and parasitic flies are rare due to specialized hosts. There is no single officially rarest fly, but many flies are rare due to habitat loss, such as some crane flies and mydas flies that are large and seldom seen. So rarest type is likely a highly endemic or parasitic fly with very small population and limited distribution, often in tropical or isolated island habitats where habitat destruction threatens them, making them rare and seldom observed by humans.