INSECTS. 255 



the perfect insect emerges to repeat the process. Natu- 

 rally these ichneumon-flies are an important agent in keep- 

 ing down injurious insects. 



The ants are possibly the most interesting of all insects. 

 They are true communists. In them, as in the white 

 ants (p. 247), there is a differentiation of the individuals 

 into males, females, and workers, the latter being wingless. 

 Any adequate treatment of these forms would of itself 

 demand a book larger than this volume. The males and 

 females take 'wedding-flights/ after which the male soon 

 dies, while the females bite off their wings and henceforth 

 have nothing to do except to lay eggs. These eggs are 

 cared for by the workers, which, as the name implies, 

 perform all the labor of the colony. They obtain the 

 food, take care of the immature insects, build the nests, 

 and carry on the wars. In their battles some ants always 

 take prisoners, and these are kept as slaves. Some species 

 of ants have depended on slaves so long that they are only 

 able to fight, while did the slaves not feed them they would 

 starve. No group of insects will better reward careful 

 study than these. 



The digger-wasps make mines in the earth or in wood in 

 which they lay their eggs, usually placing with the eggs a 

 supply of food for the young. Some use as food pollen 

 and nectar of plants, while others store up insects or spiders 

 which have been so stung that they are paralyzed, not 

 killed. In this way the food will keep for a long time. 



Some true wasps are solitary, some colonial, and in 

 the colonial forms we find again, as in the ants, males, 

 females, and workers, the workers being winged. Most of 

 these true wasps (and hornets are wasps) build nests usu- 

 ally of half-decayed wood, which they chew into a kind of 

 paper. Thus the wasps were the earliest makers of wood- 



