These insects are best seen in winter, when they are unable to live away from the mats because of the cold. These eggs are most obvious in the winter, when they contrast against the dark-green of the mat. In the summer, when the mats are more orange in color, the eggs are more difficult to see. The eggs usually hatch within a day and the larvae creep onto the surface of the microbial mat or burrow into it, devouring large amounts of the microbial cells. Within a week the larva is fully grown and it transforms into a pupa.
Metamorphosis occurs and in a matter of days the adult fly emerges.
The life cycle from adult to adult takes about two weeks. However, the adults can go partway underwater surrounded by a bubble of air which acts as insulation, so that they can feed in hotter water. The ephydrid flies are strict vegetarians, but other animals associated with hot springs are carnivores and eat the ephydrids. One common carnivore is the spider. These animals live at the edges of springs, making mad dashes out onto the mat to catch adult ephydrids.