Eyes of live specimens are often beautifully colored with iridescent and metallic color patterns. They characteristically have clear wings with black or brown patterns, making wings appear to be banded. Some are all black while many have colored patterns on their abdomens and wings. Few flies can be confused with horse and deer flies. Few other robust flies are capable of biting man and animals.
Females often lay eggs in specific locations, such as on vegetation overhanging water.
Eggs are laid in masses that darken to brown or black before larvae hatch out and drop to the ground or into water. One generation per year occurs for most species. Adult females of many horse and deer fly species are attracted to man and animals in search of a blood meal, although a blood meal may not be necessary to produce the first cluster of eggs. Males are nectar feeders and often hover at certain times of the day, presumably to attract females and maintain a territory. Larvae live in species specific habitats, although most are aquatic, semi-aquatic or terrestrial.