242 Studies in Animal Behavior 



growth ; in many species the imago takes no food 

 or need take none, before the eggs are fertilized and 

 laid; and in several forms the moiith parts have 

 become so atrophied that food taking is impossible. 

 Some insects mate soon after they emerge from the 

 pupal covering. In the May-flies, which live but a 

 short time in the winged state in order to mate and 

 deposit their eggs in the water, it is probable that the 

 imago stage would long ago have disappeared were 

 it not retained as a means of effecting the union of 

 the sexes. So also with many other insects. In the 

 winged state numerous new enemies are encount- 

 ered and many lives are lost; in the pupa stage, 

 which prepares for it, there is commonly an exten- 

 sive tearing down of old structures and the building 

 up of new ones during which the insect is helpless 

 against many enemies and parasites. There are 

 compensatory advantages in the possession of the 

 imago stage in scattering the species into new re- 

 gions, and in many other ways in the different groups, 

 but were it not for the necessity for preserving the 

 mating activities which occur in this period of the 

 insect's life-history, it is probable that the complex 

 organization of the adult state would very fre- 

 quently have degenerated, or even been lost, if it 

 had not failed to develop at all. 



The mating activities are almost everywhere 

 among the most complex performances of an ani- 

 mal's life. The opposite sex must be distinguished 

 from all other creatures and responded to accord- 



