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Tsetse flies are bloodsucking flies in the genus Glossina. These African natives are probably most famous for the trypanosomes that they carry; these pathogens can cause a variety of illnesses, most notably sleeping sickness, a disease which is characterized by extreme lethargy, leading to coma and death if not treated. Tsetse flies also have a few interesting biological traits which make them a topic of study for people in the scientific community.
A typical tsetse fly has a yellow to brown body, depending on the species, and is generally larger than a housefly. At rest, tsetse flies fold their wings over each other, a distinctive trait which makes them very easy to identify. The flies also have unusually long proboscises, which are used to suck blood from their prey. Other features of the tsetse fly, like their hairy antennae, are a bit harder to identify in the field.
The life stages of the tsetse fly are quite interesting. The females actually incubate the larvae inside themselves until they reach the third instar stage, at which point they burst out and pupate underground, developing into adult tsetse flies within a matter of hours. While the females incubate the young, they feed them with a secretion much like milk which is presumably derived from their blood-rich diets.
These flies are famous for feeding indiscriminately on the blood of other animals. Many tsetse flies actually favor reptiles, although they are perfectly happy drinking the blood of mammals as well. In all instances, the flies can pass an assortment of diseases through their blood; the parasitic trypanosomes which cause sleeping sickness can actually live in the body of a tsetse fly. In animals, sleeping sickness is known as nagana; both human and animal versions are treatable with drugs.
As a general rule, tsetse flies favor areas of high humidity with dense vegetation. In parts of Africa where tsetse flies are endemic, many people have adapted their lifestyles to avoid the fly. For example, farmers may stick to the cooler, drier uplands to reduce the risk of exposure, and livestock are pastured on higher ground as well. Travelers in areas with tsetse fly populations are typically advised by regional governments to take precautions such as sleeping under an insect net.
Incidentally, tsetse means “fly” in Tswana, an African language. As a result “tsetse fly” is a bit of a redundant statement, and some biologists prefer to drop the “fly” altogether when discussing tsetses.