70 THE CLASS OF INSECTS. 



minute llattened portion. The process of degradation here 

 •seems carried out to its farthest limit. 



Thus the degraded forms of the lower series of Ilexapods 

 take on a jNIyriapod aspect. In the more highl}' cephalized 

 Diptera, Lcpidoptera, and H^-menoptera the degraded forms 

 are modelled on a higher articulate t^-pe. The idea of a divis- 

 ion into three regions is involved. Thus the wingless forms 

 of Flies, such as the Bird-louse, Nirmas; the Bat-tick, Nycte- 

 ribia; the Bee-louse, Braida; and Chionea resemble strikingly 

 the biregional Arachnids! 



In the wingless female of Orgyia and the Canker-worm moth, 

 the head is free, but the thorax is merged into the abdomen. 

 The resemblance to the lower insects is less striking. The 

 Avorker ants and wingless Ichneumons, PezomacJms, still more 

 strictly adhere to the t3'pe of their suborder, and in them the 

 triregional form of the body persists. Among the fii'st of the 

 examples here cited we have seen the workings of a law, bj' 

 which most degraded forms of insects (and this law is exerted 

 with greater force in Crustacea) tend to revert to the worm-like, 

 or, as we may call it, the archetyjKil, form of all Articulata. 



We have seen that many winged forms mimic the groups 

 above them, whereas the wingless degraded species revert to a 

 worm-like form. In either case, the progress Is towards a 

 higher or a' lower form. The latter is the more exceptional, as 

 the evolution and growth of all animals is upwards towards a 

 more specialized, differentiated form. 



The Imago. After completing its transformations the adult 

 insect immediately seeks to provide for the pro})agation and 

 continuance of the species. The sexes meet, and, soon after, 

 the male, now no longer of use in the insect economy, perishes. 

 The female hastens to lay her eggs either in, upon, or near 

 what is to be the food of the 3'oung, and then dies. This 

 period generally occurs in the summer and autumn, and during 

 the winter the species is mostly represented by the egg alone. 

 Rarely does the adult insect hibernate, but in man}- species 

 the pupa hibernates to disclose the adult in earl}- summer. 

 The larva seldom, as such, lives through the winter. 



Reaumur kept a virgin butterfly for two years in his hot- 

 house. From this it w-ould seem that the duration of the life 



