100 Species #43: Little house fly

[urbpan]

A group of little house flies (Fannia canicularis) converged on a dog ball in the side yard.


The little house fly was 365 Urban Species #054, and on that entry there's some good natural history information, such as the fact that fly's larva is studded with spikes for swimming through semiliquid chicken manure (and I think may have been the inspiration for the monsters from Tremors). What's more interesting, and I only know a little about so far, is this insect's unique behavior. They circle and swarm in a distinctive way, sometimes indoors, males engaged in some kind of territorial display. In the above picture, a group of males are altogether on a light blue ball. An identical red ball next to the blue one had only one fly on it. When I disturbed them from there, they re-converged on a white plastic bag of topsoil. Something about the light colored surfaces seemed to be attracting them.