The flies (Diptera) have a bad rap because of the bad apples that annoy, bite and vector disease. However, many of the Diptera are harmless or even beneficial, and quite beautiful. The long legged flies in the family Dolichopodidae, are slender, often brightly metallic (green to bronze) with long legs. The adults and many of the larvae are predators. The adults feed on aphids and other small insects and can be common near large populations of aphids. Unlike annoying flies that buzz in your ear, the long legged flies will fly away (buzz off) if you get too close.
Andrei Sourakov, of the Florida Museum of Natural History, recently noted that long legged flies in the genus Condylostylus have one of the most rapid responses to light of any insect measured. In work described in Florida Entomologist, Sourakov found that his camera flash would startle the flies. By the time the shutter opened, the flash of the light had sent the flies airborne. Since the camera flash precedes the shutter opening by about 5 ms, the response time of the flies to the flash is between 2 and 5 ms.
There are over 100 species of Dolichopodidae recorded in Indiana. This one pictured below (possibly a Condostylus sp.) was on my milkweed feeding on aphids. Obviously, I did not use my flash.
Long Legged Fly
Living With Insects Blog 