After about a week, the eggs hatch and the baby yellow flies, called larvae, drop into the water. They stay in the water eating dead plants or tiny animals all winter long. Inside the pupa they don't eat. Instead they grow and change into an adult yellow fly. They are born sometime between March and August.
Most yellow flies like to be in the shade, and they stay away from bright sunlight.
Also, most are afraid of small spaces, so they won't follow you inside a car or building. But in the shade, twenty or thirty can swarm around your head and shoulders at the same time. At a fast jog, you can outrun most of them. However, once these flies find you, it is hard to make them go away. In addition to biting people, yellow flies bite wild and domestic animals, reptiles, and amphibians.