S34 SANITARY ENTOMOLOGY 



many eggs are deposited. The flies immediately return to the cow. The 

 larvas migrate from the dung when about to pupate and the puparia are 

 usually found at some distance away or under the sides of the patch of 

 dung. The horn fly in America requires about 17 days from egg to 

 adult. 



Protection of the animal from the horn fly by the use of repellents is 

 suggested. In this connection Graybill's bulletin on repellents should 

 be consulted. Dipping vats and the cattle dip of the Bureau of Animal 

 Industry (see Chapter XXXI, p. 442), now used in the control of the 

 Texas fever tick, aid materially in reducing horn fly numbers. 



Two practical methods are available for attacking the larvae and 

 pupas.. One is to throw lime on the dung, but the better method is to spread 

 out the dung so as to favor its rapid drying or to allow a number of pigs 

 to run with the cattle. In their eff'orts to obtain undigested food particles 

 the pigs will eff'ectively destroy the dung as breeding places for the fly. 



Tsetse Flies 



The tsetse flies of the genus Glossina are among the most dreaded in- 

 sects of Africa. They are the carriers of three or more types of sleeping 

 sickness, of aino, nagana, souma, horse sickness, baleri, and other 

 trypanosomiases of many domestic and wild animals. There are quite 

 a number of species, and probably all are important, but G. morsitans 

 Westwood and G. palpalis Robineau-Desvoidy, are the best known. Excel- 

 lent discussions of each of the important species and tables for differen- 

 tiation are given in the textbooks of Hindle, and Patton and Cragg. 



The reproduction in this genus is very remarkable, resembling that 

 of the Pupipara and is probably the result of their exclusively blood- 

 sucking mode of life. The female lays a single larva at a time, which is 

 retained and nourished in the oviduct until it is full grown. After the 

 larva is born it at once burrows into the ground and pupates. The larva 

 is generally of a yellowish white color and bears at its posterior extrem- 

 ity a pair of large dark-colored protuberances between which is a depres- 

 sion into which open the spiracles of the eighth segment. It pupates 

 within the puparium or last larval skin. The puparium is broadly ovoid 

 in shape and by its caudal appendages affords a means of distinguishing 

 the species. 



The habitats of the various species should be rather thoroughly 

 studied by any one expecting service in the African tropics. In general 

 the flies are found in moist forest regions, especially along river courses, 

 but the temperature, moisture, and shade requirements seem to vary 

 for the different species. 



