379 
bility is that faeces containing the parasites may be evacuated while the 
mosquito is in the act of feeding, and dropping on to some exposed part 
(in the neighbourhood of the eye or nostril, where the mosquito usually 
feeds), thus bring about an infection of the bird. We know now of at 
least one instance where a Trypanosome-infection is brought about by 
means of the faeces. If this does happen in the present case also an 
explanation would be furnished of the apparent enormous waste of un- 
encysted individuals. On the other hand, it is quite likely that, as the 
resting Flagellates would doubtless become active again as soon as fresh 
liquid (blood) reached the intestine, some of the parasites would be able 
to pass forwards into the stomach and repopulate it. There is then, 
of course, the alternative hypothesis that certain of these Flagellates 
would in turn produce inoculative forms, which could infect a bird (if 
the right host) at a subsequent meal. 
Up to the present, I have not been able to obtain experimental 
evidence to shew whether either of these possibilities actually occurs. 
It has been clearly proved, however, by Novy, McNeal and Torrey 
(l. c.) that “Crithidia” fasciculata thrives in the mosquitoes in the pre- 
sence of blood. They state that the Flagellates occurred most abun- 
dantly in the stomach at from 40 to 60 hours after feeding, having 
multiplied rapidly during this interval and “permeated” the stomach. 
(The mosquitoes used were wild ones, and were fed on pigeon’s or guinea- 
pig’s blood.) On the other hand, Patton® has pointed out that a true 
Herpetomonas of mosquitoes (C. fatigans) is readily found in the male 
individuals, but only rarely in the females, the reason being that when 
the latter are fed on blood, the parasites usually SISO PESE (after having 
been present in the larvae). 
With regard to the origin of the Flagellates in the infected hiber- 
nating mosquitoes, there are one or two interesting bionomical points 
bearing upon the question which I may mention. I was able to make a 
few personal observations during the early summer upon the relation 
between the food of the female and the development of her eggs and 
their oviposition. It is possible, however, that a distinction must be 
made in this connection between “summer”-females, which produce 
larvae during the season, and “autumn” ones, which hibernate and pro- 
duce larvae the following year. I found that the former individuals 
would always take a meal of blood (the conditions being suitable, of 
course) before being fertilized; indeed, none of the females which I have 
examined soon after a (first) meal of blood has been fertilized. This 
refers, however, to females bred in captivity and I am not at all certain 
6 Sci. Mem. Med. India, No. 53. 1912. 
