Kleine states (1912) that _Glossina palpalis_ can no longer be regarded as the sole transmitter of sleeping sickness. Taute (1911) had shown that under experimental conditions _Glossina morsitans_ was capable of transferring the disease and Kleine calls attention to the fact that in German East Africa, in the district of the Rovuma River, at least a dozen cases of the disease have occurred recently, though only _Glossina morsitans_ exists in the district. It appears, however, that these cases are due to a different parasite, _Trypanosoma rhodesiense_. This species, found especially in north-east Rhodesia and in Nyassaland, is transferred by _Glossina morsitans_. Other workers maintain that the disease may be transmitted by various blood-sucking flies, or even bugs and lice which attack man. Fülleborn and Mayer (1907) have shown by conclusive experiments that _Aedes (Stegomyia) calopus_ may transmit it from one animal to another if the two bites immediately succeed each other. It is not possible that insects other than the tsetse-flies (and only certain species of these), play an important rôle in the transmission of the disease, else it would be much more wide-spread. Sambon (1908) pointed out that the hypothesis that is spread by _Aedes calopus_ is opposed by the fact that the disease never spread in the Antilles, though frequently imported there by West African slaves. The same observation would apply also to conditions in our own Southern States in the early part of the past century. Since _Glossina palpalis_ acts as an essential host of the parasite and the chief, if not the only, transmitter, the fight against sleeping sickness, like that against malaria and yellow fever, becomes primarily a problem in economic entomology. The minutest detail of the life-history, biology, and habits of the fly, and of its parasites and other natural enemies becomes of importance in attempts to eradicate the disease. Here we can consider only the general features of the subject. _Glossina palpalis_ lives in limited areas, where the forest and undergrowth is dense, along the lake shore or river banks. According to Hodges, the natural range from shore is under thirty yards, though the distance to which the flies may follow man greatly exceed this. It is a day feeder, a fact which may be taken advantage of in avoiding exposure to its attacks. The young are brought forth alive and full-grown, one every nine or ten days. Without feeding, they enter the ground and under favorable conditions, complete their development in a month or more. [Illustration: 137. Sleeping sickness concentration camp in German East Africa. Report of German Commission.]