Tsetse, sometimes called tik-tik flies and also known as tzetze, are large biting flies that occupy much of Africa. Tsetse flies include all the species in Glossina, which are put in their own family, Glossinidae. The tsetse is obligate parasites that live by feeding on the warm blood of vertebrates. Tsetse has been widely studied because of its role in transmitting disease. They have a significant economic impact in tropical sub-Saharan Africa as the biological vectors of trypanosomes, which cause animal trypanosomiasis and human sleeping sickness.
The African tsetse fly drinks the blood of vertebrate animals, and its inflicted bite is more dangerous than it seems.
Tsetse flies may be complex in shape as they are similar to house flies. Like all insects, an adult tsetse fly has three sections: a thorax, head, and a primitive abdomen. The head contains two huge eyes on each side and a big bulb on the bottom to which is added a forward-pointing beak, or the part through which blood is absorbed. The large thorax includes three connected segments, two wings, six legs, and two crucial organs for balancing, called halteres. The abdomen is tiny but grows in size as the fly drinks enough blood to weigh twice as much as its initial weight. Most tsetse flies are remarkably tough externally. It is nearly impossible to crush one with bare hands.
Tsetse has an exceptional life cycle which may be due to the abundance of their food source. A female prepares only one egg at a time. She retains each egg within her uterus to have the child grow internally during the first three larval stages; a method which is known as adenotrophic viviparity. The female feeds the growing offspring with a milky substance secreted by a revised gland in the uterus during this period. In the last larval stage, the tsetse larva vacates the uterus and starts its independent life. The newly free tsetse larva crawls into the ground. It forms a hard outer shell known as the puparial case, in which it achieves its morphological transformation into an adult fly.
The dangerous sleeping sickness caused by the tsetse fly, is a parasitic disease located in regions south of the Sahara Desert as far as the ancient Cape of Good Hope. There are three stresses of sleeping sickness, which affect humans and beasts. West African and East African are the two strains in humans, while nagana is the form of the disease found in animals. Much African livestock suffers, and two million cows die annually as a result of infections. However, many animals that dwell in Africa can resist the disease.