LIFE HISTORY OF TSETSE FLIES 495 



especially on certain large lizards. Lloyd thinks that small mam- 



mals and birds may be important sources of food for tsetses, for, 



though these animals are usually able to avoid attacks by the 



flies during their time of activity, many of the nocturnal species 



hide during the day in the same places frequented 



by the flies and would then be easy prey for 



them. 

 Life History. -- Tsetse flies differ from all 



others of their family in their remarkable manner 



of reproduction. Not only do they not lay eggs, 



but the single developing larva is retained within 



the body, being nourished by special glands on 



the walls of the uterus. The larva is full grown 



and occupies practically the entire swollen abdo- 



men of the mother before it is born. The proc- FIG. 233. Newly 



ess of giving birth to the larva is very rapid, %$E*g. 



occupying only a very few minutes. As soon as Us. x 5. (After 



born another larva begins its development, etc. 



In Glossina palpalis the first larva is born three or four weeks after 



mating, immediately after emergence from the pupal case, and 



another is born every nine or ten days providing the temperature 

 is around 75 or 80 F. and food is abundant. 

 There is little data on the total number of young 

 produced, but in one captive fly eight larvse were 

 produced in 13 weeks and only one egg was found 

 left in the body. Pregnant flies often abort when 

 disturbed and cases are known in which the larvse 

 pupated within the abdomen of the mother, to 

 the destruction of both of them. 



The larva (Fig. 233) is a yellowish white crea- 

 FIG. 234. Pupa tare, about one-third of an inch in length, with 



of tsetse fly, Glos- " ' 



palpalis. x a pair of dark knobhke protuberances at the pos- 



5. (Partly after ^erior end of the body between which are the res- 

 piratory openings. It immediately hides itself in 

 loose soil or under dead leaves in the place where it was deposited 

 by the mother, and transforms to a pupa (Fig. 234) . The pupa- 

 tion takes place in the course of less than half an hour in soft dry 

 ground, and in an hour to an hour and a half in hard or damp 

 ground. After pupation the color begins to turn dark and in 

 four hours the pupa is a dark purplish brown color. It is shaped 



