I was out looking for the elusive snow fly yesterday but found this, instead: an eastern stonefly (Allocapnia recta), a member of the Capniidae (small winter stoneflies). At least that’s what I think it is. Larvae are active during the winter, and adults can fly and mate even when temperature is in the teens. Pretty incredible to see them flitting around on a cold day when other insects cannot even move. At Hildacy Farm in Media, PA. Probably emerged from the nearby Crum Creek.
If you’re out on a nature walk today, keep your eyes peeled for snow flies. These are essentially wingless crane flies loaded with antifreeze. This one is a male Chionea scita, I believe. Not much is known about these insects, although there is speculation that at least some members of the genus hang out in rodent burrows eating feces. (Don’t judge.) Please see “The crane fly genus Chionea in North America” (Byers 1983) for more details.
You might note that it has halteres, which is interesting because these are organs used in flight (they are modified wings … which is why flies only have one pair of wings). Would be fun to figure out whether snow fly halteres still work, though that would have to be inferred by anatomy and maybe some electrophysiological tricks. Or perhaps they serve a new function. To see photographs of some flies that have lost their halteres, check out the Braulidae (bee parasites) or Hippoboscidae ovinus (sheep ked). I love wingless flies. Did a presentation on them when I took entomology during high school … and have been creeped out and impressed by them ever since.