# Encyclopædia Britannica, Ninth Edition/Tsetse fly

From volume XXIII of the work. See also the Project Disclaimer.
TSETSE FLY (Glossina morsitans). The tsetse fly, so much dreaded by the traveller in South Africa, belongs to the sub-family Jfuscinx and is closely allied to Stomoxys. It is scarcely larger than the common house fly, which it resembles in its general shape. It can, however, be easily distinguished by its colour and the position of its wings. These are longer than the abdomen, and when at rest they project behind it, overlapping one another at their tips. This gives the fly a longer and narrower outline than that of the house fly. The colour is somewhat like that of the honey bee: the thorax is chestnut brown with four longitudinal black stripes, the abdomen light yellow with transverse bars of dark brown on its dorsal surface. The proboscis, with which the fly inflicts its sting, is grooved and contains two long styles; and it is guarded by a pair of setose palps. At the base of the proboscis is a dilated horny bulb, and in this swelling it is supposed that the poison is secreted. The bite of the tsetse is innocuous to man and is not more painful than that of a gnat. Large game, goats, and apparently all animals whilst suckling, are also unaffected by it. But to the horse, ox, and dog it is fatal. The poison may take effect after a few days, or the animal may remain apparently unaffected for some months; but eventually symptoms of poisoning appear. These symptoms seem to be rather variable; as a rule swellings arise under the jaws and around the navel, the eyes and nose begin to run, and, although the animal con tinues to graze, it becomes more and more emaciated, suffers violently from purging, and at length succumbs to extreme exhaustion. Post-mortem examination shows that the muscles, and especially the heart, are in a very soft and flabby condition. The lungs and liver are affected, the gall bladder distended with bile. The fat is of a greenish yellow colour and oily consistency, the blood small in quantity and very thin, with hardly any power of staining. At present no cure is known for the bite, nor does inoculation seem to afford any protection. The fly is said to avoid animal excreta, and in some parts a paste composed of milk and manure is smeared on cattle which are about to pass through the "fly-belts." This affords a certain amount of protection. Lion's fat is used in the same way, and is said to be efficacious.
The fly is found as a rule in the neighbourhood of water, and its habitat is usually sharply defined. Often it occurs on one side of a stream but not on the other. The limits of the "fly-belts" are well known to the natives, and travellers can ensure comparative safety to their cattle by passing through these districts after sun down. The northern limits of the area inhabited by the tsetse are not known. It is found throughout the valley of the Limpopo river, but does not come much south of this, except in the eastern borders of the Transvaal. Here it extends far south of Delagoa Bay, and infests the Lobombo Mountains and the Amatonga country, reaching to the confines of Santa Lucia Bay. It appears to be gradually retreating northwards, following the big game.
The fly is figured in Proc. Zool. Soc., 1850, and by Frank Gates, Matabele Land and the Victoria Falls, 1881.