THE SPECIAL SEXSKS 



39 



species have boon known to appear at the windows of 

 rooms in which the females wore in captivity. Xow in 

 these moths the antenna 1 of the males are hiirhlv (level- 



o t> 



oped. It seems undoubtedly to be the case that since 

 the males could not see the females, they discerned them 

 through the sense of smell. And this is further evi- 

 denced by the antenna 1 , the seat of smell, being' more 

 fully developed in the males than in the females. 



In the growth and development of insects, we have 

 found that at different stages the strnctnrc of the insect 

 and the food habits are different. The butterfly has a 

 long very lender tube through which it secures its 

 liquid nourishment. It has no jaws with which to mas- 

 ticate the leaves of plain-. The caterpillar which 

 hatches from the egg of this very butterfly has jaws 

 with which to eat. It has also specially formed tastes 

 for certain plant tissues. If the eggs arc deposited in 

 places remote from the proper food plants the young 

 caterpillars will starve, since they have no "taste" for 

 oilier plants and will not cat them. The parent, then, 

 must be able to recognize the proper food plants upon 

 which or near which to deposit her eggs. Her sight, as 

 we shall see presently, is imperfect, and does not clearly 

 recognize the various forms in plants. She cannot 

 taste the plant leaves, and in many eases there are no 

 nectar-bearing blossoms to aid her. Plants give off 

 characteristic odors, and it is upon these she evidently 

 depends for the recognition of the plants furnishing 

 proper nourishment for her young. 



The Production of Odors. Many caterpillars emit offen- 

 sive odors. (See pp. 16, 17.) Certain insects, such as 

 the well known "stink-bugs" (Fig. 45), give off, when 



