452 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1923 



the gnats and mosquitoes, and in these forms have been described 

 as containing rods similar to the scolopalse. Some writers believe 

 that these are organs of hearing. 



Our ignorance or lack of exact knowledge of the senses of insects 

 in general suggests that the next important line of investigation in 

 entomology should be in the direction of a study of their psychic 

 activities, call them tropisms, or what you will. A more intimate 

 understanding of the senses and perceptive powers of insects is 

 important scientifically and practically as leading to a more intel- 

 ligent development of methods for combating those species that are 

 inimical to us. 



