In the last post I had a photograph of Bombylius major. That fly looks soft and furry, almost like a deer mouse. It even has a lighter belly–similar to the countershading exhibited by the mouse.
A few flies have enough hair to almost seem like small mammals. This Scatophaga, for example:
Some are almost naked, like this Myimyrmia fenestrata, which belongs to the fruit fly group.
Some have an intermediate amount, as can be found on this robber fly, Efferia alibarbis.
Why are some so hairy? I think it does have something to do with thermoregulation, but exactly how, I don’t know.