23 



great care be taken to protect them from injury, this hair is very 

 frequently more or less rubbed off, with the result that the 

 appearance of the specimens becomes much altered. The species 

 of Simulium are difficult to distinguish one from another, but useful 

 distinctive characters are sometimes afforded by the legs. Within 

 the last three years Mons. E. Roubaud has divided the genus into 

 the two subgenera Pro-Simulium and Eu-Simulium, according as 

 " the second joint of the hind tarsi in both sexes is elongate, linear, 

 and without a basal notch " (Pro-Simulium), or " short, curved, 

 and dorsally notched at the base " (Eu-Simulium). Furthermore, 

 in Pro-Simulium the pupae are said to have a very large number 

 of respiratory filaments, while the cocoons are incomplete and 

 collected in clusters ; in Eu-Simulium, on the other hand, the 

 number of the respiratory filaments in the pupa is usually small, 

 and the cocoons are solitary, and complete.* 



jj^The males of Simulium are incapable of sucking blood ; the 

 females however are, by day, voracious blood-suckers, inflicting 

 a very severe bite, which leaves behind it an irritating wheal. Since 

 they often occur in enormous swarms, they are frequently a terrible 

 scourge to human beings and domestic animals. With reference to 

 a species of this genus at Bonginda, Lulanga River, Upper Congo, 

 Congo Free State, the Rev. W. D. Armstrong, of the Congo Balolo 

 Mission, wrote as follows in October, 1907 : " Native name N'kuti : 

 known among white people as sand-flies. These are very abundant 

 all over the Lulanga River district ; they do not appear at night, 

 and are more numerous in the early morning than at any other time 

 of the day. They fly low, and annoy the natives by biting their 

 feet and ankles, drilling a small hole in the skin through which 

 they draw blood. After the operation the mouth of the hole is 

 seen plugged with a tiny drop of blood ; the bites itch very much." 

 Of an undetermined species of Simulium met with at Leopoldville 

 and other localities in the Congo Free State, by the members of the 

 Expedition of the Liverpool School of Tropical Medicine to the 



* Cf. E. Roubaud, " Apertjus nouveaux, morphologiques et biologiques, sur les 

 Dipteres piqueurs du groupe des Simulies": Comptes Rendua Hebdomadctires des 

 Seances de I' Academic des Sciences, T. CXLIIL, pp. 519-521 (1906). 



