Flight and Attraction of Mosquitoes 107 



stronger the speed of the returning Anopheles 

 increased. The termination of both forward and 

 return flight was remarkably abrupt, or as one ob- 

 server expressed it, "the flight stops with almost 

 mechanical precision when there is too much 

 daylight or too much darkness. " 



As already mentioned, the Anopheles travel at 

 incredible speed toward the end of the return 

 flight. The only change taking place was the 

 increasing intensity of light. This, together with 

 the fact that when sheltering from the wind or sun- 

 light they will remain hungry rather than fly 

 three feet out into the sunlight to bite a person 

 standing in the sun, but will immediately attack 

 him if he steps into the shade, is at least sug- 

 gestive. Are both heat and a certain intensity 

 of light repulsive to Anopheles, or is it the light 

 only ? The latter would seem to be the case under 

 natural conditions, as they do not come out into 

 the sun to bite after 7.00 a.m. One of the obser- 

 vers, Mr. Zetek, noted some males in the return 

 flight, and also found blood in the mosquitoes 

 returning. 



During the flight observations Mr. E. F. Quimby 

 conceived the idea of using an apparatus for 

 registering the direction of the flight of Anopheles 

 with a view to determining the direction of, and 



