The adults are pollen or nectar feeders. The larva which eat a mixture of rotting vegetable and animal matter are unusual in having their skin thickened with calcium carbonate. Dance flies look and act like Robber-flies. They can be distinguished by their less bulging eyes and the lack of the trough between their eyes, and the fact that their larva are carnivorous as well as the adults. They are called Dance flies because they can often be seen flying low over the water in a twisting spiraling manner that to our eyes looks much like a dance.
Dance flies are also of interest because of their courtship.
Because of their predatory nature the males often feel it is advisable to offer the female a gift of food to keep her occupied while the mating is occurring. In the least complicated species the male simply offers the female an insect he has caught. In more advanced species the male wraps the gift in a ball of cotton spun from special glands in his front legs, and in some decadent species the male offers the female an empty ball of silk safe in knowledge he will have done the deed and escaped before she catches on to his deception. The Cyclorrhapha These are the most evolutionarily advanced flies with mostly maggot like larva. They are generally short and stocky and covered in short hairs.