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 K"oe 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, Peryassii 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 veiy 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 



