THE H\MENOPTERA. 263 



and tliey are not incomplete in the usual sense of the term, for 

 there is a marked distinction between the three stages of growth. 

 The nymphs have not the same powers and structures as the 

 adults. The Cynips aptcra never has wings ; the transformation 

 is imperfect, and the evolution of the insect does not reach the 

 point usually attained by the other Hymeiioptera. Wings would 

 be of infinite use to the Cynips, and it does not appear that there 

 is anything relating to the natural history of the species which 

 would account for the loss of wings by disuse during many suc- 

 ceeding generations. The wingless condition and the imperfect 

 metamorphosis probably have a deep signification, and these 

 exceptional Hymcnoptcra may be the oldest of their order ; for 

 it will be shown, in succeeding chapters, that there is great reason 

 for believing that wings have been superadded to the earliest 

 insects during the long geological periods. 



Nothing can be more diverse than the development and in- 

 stinctive powers of the larvae of the saw flies, the parasitic 

 Hymmoptcra, and of the ants and bees ; and it is remarkable 

 that the very imperfect larvae of the last two kinds should be 

 transformed into much more intelligent adults than the others. 

 The examination of the structural changes which occur in the 

 nervous system during the transformations of the bee, and which 

 have been noticed in Chapter III., will suggest that the concen- 

 tration of the nervous masses in the adult has much to do with 

 the development of great power of instinct. The occurrence of 

 parthenogenesis in Cynips, and in some of the wasps and bees, 

 has been proved ; and it has been noticed that the workers or 

 wingless adults are probably the result of this process. They are 

 without the power of reproduction, and thus their metamorphosis 

 is a stage more imperfect than that of Cynips aptera. 



Very little of the intense activity and instinct of the Hymen- 

 cptera appears to be squandered upon the pleasures of the adults, 

 and every unusual gift and habit they may have, with nearly all 

 their restless industry, are employed in one direction — in per- 

 petuating the species and in preserving the young during their 

 transformations. All the honeycomb making, the excavation of 

 nests, and the building-up of subterranean edifices, are for the 

 preservation of the feeble larvae and still more helpless pupae. 



