A tsetse fly, which is sometimes called a tzetze and tik-tik, is a large, biting fly. They are close in resemblance to horse flies, but have other distinctive features about them. There are 23 species of tsetse flies. Tsetse flies bend their wings when they are resting. One wing usually rests over top of the other but both covers the abdomen area. The insect originated from the mid-continental Africa and the Kalahari deserts. It feeds on the blood of animals and primary biological vectors of Wuchereria bancrofti. The fly can cause illnesses such as trypanosomes, elephantiasis and a sleeping sickness in humans. Diseases transmitted by these insects kill thousands of people each year. The flies are known to produce four generations in one year and over 31 in a life time.