134 Psyche [December 
Stegomyia scutellaris 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 2 2 of this species and Culex fatigans 
any more than water. Howlett’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 Ties 
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 
