Monday, May 31, 2010

Snipe Flies

Animal populations fluctuate from year to year and every once in a while a particular species will show up in great abundance. Whatever regulates the population size of the Golden-backed Snipe Fly, Chrysopilus thoracicus, has worked to produce this insect in record numbers this year. I can’t remember ever seeing these flies in numbers as great as they are right now.

This is a male. The most noticeable male trait is a set of enormous eyes. In fact, the head doesn’t seem to be anything but eyes. The males also display a tapering, up curved abdomen.

The eyes of the female are much smaller. This makes me think that the large eyes of the male must be used to find females. If the large eyes were necessary for searching for food or watching for predators, both sexes should have them. The abdomen of the female is also wider and doesn’t really taper until it reaches the end. Both sexes display the bright yellow spot on the thorax.

This fly seems to spend a lot of time sitting on top of low growing vegetation. They tend to stay in the shadows in low lying areas near creeks or drainage ways. They’re usually easy to spot and when disturbed normally only fly a short distance.

There’s more than one species of Snipe Fly lurking in the shadows. When I first saw this fly, I thought it might have just worn off its golden spot. A closer look quickly proved that assumption to be wrong.

I don’t know what species this. The coloration really makes the wing veins stand out. The keys probably don’t even talk about wing vein patterns.


  1. I love these guys! I appreciate the info on how to sex them, I didn't know about that.