CHAPTER V. 



Comparative Classification of Corresponding Generations of 

 Cynipidae according to their Organization. 



The activity of the fly culminates in the act of 

 oviposition ; care for its progeny occupies the whole 

 period of its individual existence. I began therefore 

 by giving a description of the complicated apparatus by 

 which egg-laying was carried out, and I now proceed 

 to compare the whole organization of the two genera- 

 tions in the various stages of imago and larva. I have 

 already described in detail the outward configuration 

 of the gall-flies, and the differences in colouring, sculp- 

 ture, and pubescence which they exhibit. 



Outward characters are usually of little distinctive 

 value in gall-flies ; a uniformly dull colour prevails in 

 almost all species ; and there are many which cannot 

 be distinguished from each other by an outward examina- 

 tion of the flies only. In comparing two alternating 

 generations, colouring counts for little ; their form, 

 structure, and size are of much greater significance. 

 In these respects there are very important differences 

 in the two generations. If a Neurotcrus and its 

 corresponding Spathegaster form be compared with 



