SOME WINGLESS INSECTS 173 



winglessness is accompanied with a total suppression of the 

 preparatory stages. 



Insects which may be regarded with any degree of proba- 

 bility as primarily wingless, are relatively very few when com- 

 pared with the whole class. It is of importance to notice 

 that in those which may be regarded as distinctly primitive 

 (the Machilidae) there is a definite, though inconspicuous, 

 process of change in the course of growth. From this fact 

 we gain perhaps a suggestion as to the existence of some such 

 process in the life-histories of the ancient, ancestral insects, 

 from which the startling transformations of their modern 

 descendants may be regarded as having been elaborated. 



