Flightless flies would seem to be an oxymoron, but there are plenty of them, and they include some of the most bizarre insects on Earth. Just search, for example, for “phorid” on this site. Some of these creatures are so bizarre, as either larvae or adults, that you’d never take them to be flies.
Get a load of this one. Matthew Cobb called my attention to a new post by the talented photographer and entomologist Alex Wild on his photography website (see also his great website Myrmecos) showing the larva of a syrphid fly so weird that it was once described as a mollusc (see caption below taken from Alex’s site). It preys on the brood of ants, and I suspect the “tube” at the upper right is for respiration (my Drosophila have a pair of these “spiracles” at their posterior end):
As lagniappe, here’s a couple of very weird flightless flies from site “The Atavism” (and indeed, vestigial wings are atavisms). Remember, these are flies.
Here’s a “sheep ked,” a parasitic flightless fly from New Zealand with The Atavism’s (TA’s) caption:
Flies in the family Hippoboscidae are blood suckers. Many of these parasites fly from hosts to host, but a number of species have become so intimately associated that they’ve given up on flying – moving from one animal to another only while those hosts are in physical contact. The flightless hippboscids are generally called “louse flies” or “keds” and the most well known examples include species that specialise in drinking from pigeons, cattle and sheep.
Note the vestigial, useless wings: a testimony of its evolution from a flying ancestor:
A parasitic bat fly, again with TA’s caption:
The bat flies have lost their eyes as well as their wings, by have made up for those loses in other body parts. The massive spider-like legs end in tiny claws that let the flies grip on the bat’s fur and move about. Once stuck on a bat these flies drink blood.
Photo by Giles San Martin
Look at those claws!
And here’s a bat fly from Kenya:
As far as we know, the family Mormotomyiidae is represented by a single species (Mormotomyia hirsuta) which is only known from a particular site in on one mountain in Kenya. As you may have guessed the site is a bat roost, and the animal, despite being only distantly related to the other bat flies discussed above, has taken on the spidery form that is associated with flies that spend their lives with bats.
You’d think this was an ant or something, wouldn’t you? We know it’s a fly because of its other traits that place it clearly with dipterans (and certainly molecular analysis would confirm that).
There are more of these; go read about them at The Atavism.
h/t: Alex Wild (who’s given me blanket permission to reproduce his work) and Matthew Cobb