658 - Heredity and Evolution 



of the female reproductive tract, before each 

 egg becomes covered by its shell. Moreover, 

 many insects possess special chambers, semi- 

 nal receptacles, where the sperm derived 

 from one copulation may survive for some 

 weeks, fertilizing new batches of eggs as they 

 reach maturity. 



Among insects, which include a great ma- 

 jority of Arthropoda (and of any other ani- 

 mals, too), the development of wings ex- 

 tended the range enormously and led to 

 tremendous diversification of the species 

 (Table 32-1). The vertebrate type of wing, 

 such as is displayed by birds and bats, rep- 

 resents a highly modified forelimb (Fig. 29-1), 

 but this is not true of insect wings. The 



insect wing essentially represents an outfold- 

 ing of the chitinous integument. It is cleverly 

 hinged at the body junction and it is oper- 

 ated by an intricate set of striated muscle 

 fibers, which are the fastest acting in all na- 

 ture. Insect wings, however, are highly diver- 

 sified as to form and function, as is indicated 

 in Table 32-1. 



Insect Societies. Most insects are non- 

 social; that is, each individual shifts for itself. 

 Males and females associate only for mating 

 and the parents have little or no concern for 

 the next generation, aside from laying the 

 eggs. However, a few nonsocial forms (for 

 example, earwigs, crickets, roaches) may 

 guard the eggs and young. 



Table 32-1— Familiar Orders of Insects 



