134 



Psyche 



[December 



Stegomyia scuiellaris were attracted by the hot air radiating from 

 a test tube filled with hot water. On the other hand, shed blood 

 and sweat did not attract the 9 9 of this species and Cule.r fatigans 

 any more than water. Hewlett's experiments were not known to 

 me at the time when these observations were made, and since they 

 were obtained independently of other observers, and the phenom- 

 enon was not known to apply to Anopheles, I may briefly report on 

 them here, especially as data on thermotropism in insects are very 

 scanty. The Anopheles which were kept in lamp chimneys for 

 other purposes, were fed on apple jelly which was spread out on a 

 glass plate. In order to prevent the mosquitoes soiling their legs 

 and wings, the jelly was covered with filter paper. In the inten- 

 tion of providing a food as natural as possible, I heated the apple 

 jelly on the glass plate, assuming that it would then be taken more 

 readily. This was in fact the case. The mosquitoes came quickly 

 to the filter paper and would bite through it as if it were human 



Fig. 2. Arrangement used in demonstrating the thermotropism of mosquitoes. 



skin. The question suggested itself whether they were attracted 

 by the odor of the jelly or, possibly, by the heat radiating from it. 

 Being curious whether the mosquitoes would be attracted also by 

 heat alone, I substituted for the glass plate which was covered with 

 jelly, a clean one which was heated to a degree fairly above human 

 body temperature but, of course, not excessive, and covered with 



