Transmission occurs through the mouthparts which are designed to cut the skin. Tsetse flies are dark in colour, look similar to house flies and are almost entirely confined to sub-Saharan Africa. G. mortisans prefers open savanna environments whereas G. palpalis is more riverine in preference. In fact, they are of as much concern agriculturally as medically with infected flies rendering millions of square kilometres of land unusable for cattle-rearing. Both sexes of fly feed on blood and transmission to and from the fly takes place through mouthparts designed for biting.
Flies feed during the day.
Eggs are are not laid but develop in utero to give rise to a larva heavier than the fly itself, i.e., flies are larviparous . Larvae burrow about 4 cm into the soil and pupate immediately. They can also infest the burrows of rats and armadillos. Both sexes feed at night on blood using piercing and cutting mouthparts. Up to a third of a gramme of blood can be consumed per feed.