TIME OF ACTIVITY 209 
Anopheles for stables. The size and number of animals exercise a strong at- 
traction upon the Anopheles, and the even warm temperature within the stables 
is probably another influence. 
Anopheles females will feed upon other substances when they can not obtain 
blood. Grassi states that Ficalbi has seen them sucking the juices of fruits and 
the filth in out-houses. Grassi and Noé have surprised Anopheles feeding upon 
unripe ears of Indian corn and sucking green grasses; they have noted that they 
would, in time of need, absorb dirty water and they have seen them attracted to 
sweetened water. 
Grassi states that Anopheles first sucks blood two or three days after emerging 
from the pupa and that in cool weather a longer time passes. Darling, in 
Panama, found that they would bite after 24 or 48 hours. Peryasst states that 
Anopheles argyritarsis and A. albimanus will sometimes suck blood ten hours 
after emergence. Many observations show that Anopheles suck blood frequently 
under favorable conditions. Neiva made careful experiments on this point and 
found that the various Brazilian species would suck blood at intervals of 24 
hours or even more frequently. In Italy it has been observed that the Anopheles 
fed upon successive days even when they had not fully digested the previous 
meal. Neiva noted that weather conditions had a marked effect on the activity 
of Anopheles. When there is a change of weather and rain threatens the Anoph- 
eles are numerous and bloodthirsty. During rain they remain quiescent but 
become active afterwards, even if a heavy rain has fallen for some hours. Neiva 
found that on very hot days the Anopheles also attacked with great ferocity. 
Little is known of the feeding habits of the male Anopheles. Grassi thought 
that the males normally feed on the juices of fruits and he has kept them alive 
on this food for 25 days. It is probable that the males of Anopheles suck the 
honey of flowers, as do those of other mosquitoes. There are several records of 
Anopheles visiting flowers but the sex is not mentioned and it is probable that 
the females also resort to flowers when their normal food fails them. 
NOCTURNAL AND DIURNAL HABITS. 
Most of the Anopheles fly preferably at twilight. This fact was turned to 
practical account in the first anti-malarial work in Italy. Grassi found that, 
while occasionally Anopheles will bite during the day, their time of normal 
activity is at twilight, and in reality very short. He observed that on un- 
clouded days, during June, July and August, the period of greatest activity 
lasted from 30 to 40 minutes and they would disappear before the obscurity be- 
came complete. At first they would come in small numbers and these increased 
until the maximum was reached after about 20 minutes; then they would again 
decrease in numbers. On cloudy days they would come earlier and remain 
longer, the governing factor being the amount of light. The Anopheles would 
appear when it was still light enough so that one could read easily, and when it 
became so dark that it was hardly possible to read the Anopheles disappeared. 
The Anopheles were active both during the evening and morning twilight but 
their number was much greater in the evening. In some cases a certain number 
