CHAPTER IV 



The Senses of Insects 



It is obvious that most insects possess a well-developed power of 

 sight. It is not believed that they have the ability to form images 

 of objects, in other words to " see," with the precision of higher ani- 

 mals. To a limited extent the compound eyes probably give an insect 

 certain powers of forming images up to a short distance — not 

 more than a few feet. They undoubtedly are well adapted to discern 



movement. The ocelli, or simple eyes, 

 are fomied somewhat on the plan of the 

 human eye ; but the lens is of fixed focus, 

 and the number of nerves in the retina is 

 comparatively small. 



The sense of hearing is well known to 

 exist among many insects. The location 

 of the auditory apparatus has been de- 

 termined in certain species. Thus, the 

 antennse of some insects are known to 

 have auditory functions ; grasshoppers 

 have an " ear " on the first segment of 

 the abdomen; other species have a 

 similar organ on the foreleg. 

 Most insects have a sense of taste. The hypopharynx, or tongue, 

 and short appendages attached to the maxilla?, or lower jaws, are 

 commonly the seat of this sense. 



There is abundant evidence of the existence of a sense of smell. 

 In fact this sense is particularly well developed in many insects, and 

 serves to guide them to their food, to lead the females to the proper 

 plants on which to deposit their eggs, and often to bring the male to 



16 



Fig. 15. — Tongue of a cricket. 

 Enlarged and natural size. 

 Original. 



