THE SENSES OF INSECTS. 



By N. E. McIndoo, Ph. D., 

 Insect Physiologist, Bureau of Entomology, Washington, D. C. 



[With 1 plate.] 



Insects, like all other animals, acquire their information concern- 

 ing the world through their senses, and this is accomplished by 

 means of impressions or stimuli affecting the sense organs. The 

 world to us is chiefly a world of visions or sights ; all the other senses 

 are secondary, and one of them — i. e., the sense of smell — is so rudi- 

 mentary that it is no longer comparable to the same sense in some 

 other animals. The world to a bloodhound is chiefly a world of 

 scents, odors, or smells, and in this case the other senses play a sec- 

 ondary place, and the world to such insects as ants and bees is not 

 onty a world chiefly of smells, but the olfactory sense plays such an 

 important part in their lives that should it be suddenly destroyed 

 these insects could no longer exist. Thus an individual's world is 

 determined principally by his most important sense, i. e., we gain 

 most of our knowledge through our eyes, while a blind man acquires 

 most of his knowledge through the senses of hearing and touch, 

 which are closely allied. Every person lives in a world somewhat 

 different from that of an}' other person, and reasoning along this 

 line there must be as much difference between our world and the 

 insect world as there is between day and night. Now let us briefly 

 discuss the various senses of insects in order to determine the nature 

 of the insect world, but it must be remembered at the outset that we 

 are liable to misinterpret their activities, because the best that we 

 can do is to compare under similar conditions their behavior with 

 ours, and since insects are developed so differently from us, we really 

 have no right to make such comparisons. 



THE SENSE OF SIGHT. 



Insects have two kinds of eyes, simple and compound. On most 

 species both kinds are found, on some either kind alone, and in a 

 few no eyes at all. The most primitive living forms and the larvae 

 of the specialized insects (those with complete metamorphoses) have 



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