145 



very abimdaiit on the lielgian bank, wliicL is low and wooded, 

 and that there are plenty in the various islands in the Ubangi, 

 and it is here that the specimens mentioned were captured. G. 

 palpalis is stated to be very common in the Bangala country, 

 not common in the Bondjo country and fairly common in the 

 Mbaka country and in the region between Bangi and Fort-de- 

 Possel, but scarce between this latter place and Mobaye. 



Tables are given showing- the relation of cases of sleeping sick- 

 ness in the various divisions of the country and the author points 

 out that there is no sort of parallelism between the distribution 

 of the tsetse and the intensity of the disease. He is, therefore, 

 led to suppose that possibly some other blood-sucking insect may 

 be concerned and he gives the following as the result of his 

 observations. 



Cidex and Mansonioides are very common from Bonga to 

 liiranga, but become scarce at Impfondo ; from Dungu to Betu 

 only Cidex was found, and these in quantity. From Betu to 

 Bangi there were no mosquitos, though they reappeared at this 

 latter place, but were much less numerous there than at Bakundu 

 and Kemo or Fort-de-Possel {Culex and Mansonioides). There 

 were a few mosquitos at Bessu and of the same species ; at Kwango 

 the number increased and Anopheles was taken for the first time. 

 These three genera are not abundant between Kwango and Mobaye, 

 but many Anopheles were found in the villages near the lattei 

 Station. The author noted that when AnopJieles began to be 

 taken cases of paludism also appeared, and of some hundreds of 

 children examined nearly one-third had enlarged spleens and 

 numerous haenuitozoa in their blood. Sfo/iioxj/s is unknown to 

 the natives and the author did not meet with one between Bonga 

 and Betu. At Betu they are very scarce, but from that place tO' 

 Bimbo they begin to be very abundant. From Bangi a good 

 number of Stonw.fi/s was found until Fort-de-Possel was passed, 

 and there they were fairly numerous both on the river banks and 

 in the villages. They are entirely absent at Kwango. Only 

 a small number of Tabaxidae were seen in the districts of Bonga, 

 Lukolela and Liranga ; they are scarce above Bangi. Some 

 Haeniatopota were taken at Bimba. Simulitdae were abundant 

 in the great epidemic centres of Bimbo, Takoli, Bogassi and 

 Mongumba. Xone were found at Ikumba, which is also a great 

 sleeping sickness centre near those just mentioned. These insects 

 only bite at nightfall, between 5 and 7 p.m., and in the early 

 morning from sunrise to about 8 o'clock. Larvae of Avclime- 

 romyia luteola are found in all the riverside villages. 



The author says that the above facts are more or less contra- 

 dictory and that the relationship between the distribution of 

 biting flies and sleeping sickness in this area is somewhat difficult 

 to understand. He considers that there is no longer any question 

 that sleeping sickness can pass into and across districts in which 

 there are no tsetses ; whereas in those districts where Glossina is 

 comj)aratively abundant, as at Bonga and Lukolela, it would 

 appear that this fly plays a part in the distribution of tlie disease 

 almost to the exclusion of all other biting insects which live 

 rather in the villages than in the bush. 



