PHYSIOLOGY OF WING DEVELOPMENT IN APHIDS. 



TABLE II. 



103 



any of the wing-producing substances. Thus, it is evident that 

 there exists a variation in the degree of susceptibility among the 

 species of aphids. 



It might also be well to add here that in several species of 

 aphids belonging to the tribe Chaitophorini no apterous vivip- 

 arous females have as yet been found. Such, for example, is the 



