Tsetse flies (Glossina spp) are classified in a mono­ generic taxon of 32 species and subspecies, the Glossinidae. Most unusual and interesting insects, tsetse are confined to sub-Saharan Africa, but fossils from the Oligocene have been found in North Amer­ica. Tsetse flies have an extremely low rate of reproduction. Females require two weeks to develop, and deposit their first mature larva, which almost immediately burrows into the soil and pupates. Additional larvae are produced maximally at ten-day intervals in well-fed flies. Thus tsetse are K-selected insects, and mortality rates must remain low if tsetse populations are to continue.