THE YELLOW-FEVER MOSQUITO 109 



and O. Neumann — in Brazil, at any rate — ^they 

 are capable of biting not only during the twilight, 

 but at any times. The bite lasts twenty to thirty 

 seconds, after which the mosquito rests a bit, 

 waving its third pair of legs in the sun. After 

 this rest she flies away to some sheltered spot, 

 and whilst blood is being digested the mos- 

 quito takes nothing but water — a very proper 

 dietetic measure. After three or four days 

 the female is ready for another meal. 



In the absence of man these mosquitos 

 will suck blood from other animals, and in 

 confinement they are generally fed on rats 

 or canaries, and they will even suck up a 

 drop of blood presented on a piece of cotton- 

 wool. 



If the female mosquito has been fertilised 

 before the sucking of blood she will commence 

 egg-laying two or three days later, and two or 

 three days later again the larva will emerge. 

 The larval stage lasts from nine to twelve 

 days, and the pupa stage three to four, so that 

 the whole metamorphosis takes from sixteen 

 to twenty-two days. Hence, during warm 

 weather, many generations succeed each other, 

 but one must have a temperature of at least 

 20° to 27° C. Below that temperature the 

 processes tend to slow down, and under a 

 temperature near freezing-point the regular 

 development is definitely interrupted. But 



