THE HYMENOPTERA. 263 
and they 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 Cyzips aptera never has wings; the transformation 
is imperfect, and the evolution of the insect does not reach the 
point usually attained by the other AZymenoptera. Wings would 
e of infinite use to the Cyzzps, 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- 
eeding generations. The wingless condition and the imperfect 
metamorphosis probably have a deep signification, and these 
exceptional Hymenoptera 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 larve of the saw flies, the parasitic 
Hymenoptera, and of the ants and bees; and it is remarkable 
that the very imperfect larve 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 Cyzzps, 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 moré imperfect than that of Cynzps aptera. 
Very little of the intense activity and instinct of the ymen- 
optera 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 pup. 
