Adults of extant forms are principal vectors of sleeping sickness.
Females are larviparous.
After the larva is laid on the ground, it immediately pupates. The current distribution of the family is restricted to the African continent, though the fossil record of these flies is known only from the Oligocene of the North American continent. Many workers have postulated the fly's possible hosts in the geologic past and various reasons for such a disjunct distribution. When their big bloodbanks vanished, they turned to the nearest available substitute, the alligator.