PROPHYLAXIS OF MALARIA. 
49 
of importance in prophylaxis. It may be stated that while many 
species of anophelines are of sylvan character, all of the species that 
have come in contact with man and have continued in association 
with him are bloodsuckers, and that, even in the sylvan species, 
blood is a normal food, being obtained from other animals than man. 
It is not true that a meal of blood is necessarv to the female before 
depositing her eggs or, as has been stated, that the fertilization of 
the female is impossible unless she has sucked blood. Grassi found 
that Anopheles will bite large animals in preference to small ones—a 
horse being bitten in preference to a man—and that they bite in 
the open as well as in habitations. The first meal of blood is taken 
two or three days after the insect emerges from the pupa, as shown 
bv Darling and Grassi, and thev will bite at intervals of a few hours. 
It is well known that during rains it is seldom that one is bitten 
by anophelines, but that after the cessation of the shower they are 
very vicious. This is especially noticeable in the Tropics during the 
rainy season. The effect of temperature upon the feeding habits is 
also very marked, a high temperature apparently stimulating the 
biting propensities of most species of anophelines. 
The time of day in which the anophelines bite is an important pro¬ 
phylactic point. Most species of the Anophelince fly during the 
twilight hours, and it is during this time that one is most frequently 
bitten. While this is true, I have seen various species of Anopheles 
biting in the late afternoon, and M yzomyia funesta , a common ma¬ 
laria mosquito, biting in the early morning and even at noon in 
the Philippines. 
Anophelines will bite during the night if the temperature is high, 
as in the hot portions of the Middle West, but where the nights are 
cool, even though they may be present in great numbers, they bite 
only during the twilight hours and in the early morning. A beau¬ 
tiful illustration of the twilight habits of the anophelines is noted 
in the observations upon the Canal Zone regarding the flights of 
Anopheles , in which it was found that the flight of these insects from 
the propagation area to the town began about 6.30 in the evening 
and that it ceased before 9 in the evening, while the return flight 
began at 6 o’clock in the morning and lasted about half an hour. 
After biting, the anophelines usually hide out of doors, within a 
short distance of habitations, beneath tall grass, or within the foliage 
of bushes and trees. However, they often remain within the habita¬ 
tion, and I have observed hundreds of anophelines in the daytime 
around the baseboards of toilet sinks and upon clothing in dark 
closets in the Philippines. 
While, as has been said, most anophelines prefer the twilight 
hours for biting, they will bite at any hour of the day. Chagas and 
Neiva l5 , Smith 10 , and Howard 17 all have recorded distances in which 
58000°—14-4 
