LIFE HISTORY OF PHLEBOTOMUS FLIES 469 



could not penetrate. The eggs are elongate and are of a dark, 

 shiny brown color, with fine surface markings which vary in 

 different species (Fig. 214). 



The incubation in the case of the common Old World P. 

 papatasii requires from six to nine days under favorable con- 

 ditions, but the eggs are very susceptible to 

 external conditions, and die quickly if ex- 

 posed to sunlight or if not kept damp. The 

 larvse (Fig. 212B) are tiny caterpillar-like 

 creatures with a relatively large head with 

 heavy jaws (Fig. 215), and with two pairs 

 of bristles on the last segment of the abdo- 

 men, one pair of which are sometimes nearly 

 as long as the body and are held erect and 

 spread out fanlike; in the newly hatched p IG< 214. Eggs of 

 larvae there is only one pair of bristles. The phiebotomus flies; A, P. 



,,. i i -.LI xii papatasii; B, P. argen- 



body is provided with numerous toothed t i pes; c, P. minutus. 

 spines which give it a rough appearance, x about 200. (After 

 These spines have recently been shown by 

 Howlett to differ in different species and, together with the rela- 

 tive length of the caudal bristles, to form good identification 

 marks. The whole length of the larva of P. papatasii when 

 full grown is less than one-fifth of an inch, and is therefore not so 

 large as an ordinary rice grain. It is 

 quite active in spite of the fact that it 

 has neither legs nor eyes; it progresses 

 in the manner of a caterpillar, holding 

 to a rock or board with the tip of the 

 abdomen while stretching the body, then 

 hiding with the doubled-under head while 

 drawing up the body again. It feeds on 



FIG. 215. Front view of , . , , , j i i i 



head of Phiebotomus minu- decaying vegetable matter, and probably 



tus larva. Much enlarged. a lso on moulds, etc. When exposed to 



light the larva of P. papatasii has the 



peculiar habit of flicking itself off the surface on which it has 

 been resting. On approach of danger, Phiebotomus larvae often 

 " play 'possum " and feign death. 



The full development of the larvae requires from three weeks 

 to two months or more, depending almost entirely on the tem- 

 perature. Larvae which hatch at the beginning of cold weather 



