GENERAL SUMMARY. 185 



GENERAL SUMMARY. 



A review of what has been advanced m the foregoing 

 chapters lead to some conchiding remarks. 



The Homoptera occmTed very early in geological 

 times, and the stridulating Tettigidae fm^nish us with 

 the first examples of the group. The earliest forms 

 as they appear in the rocks are already highly special- 

 ized, and the species in many instances are as large as, 

 and in some larger than, the known recent forms of 

 Europe and Africa. 



The record of fossil insect-life is very defective, from 

 the nature of the remains and the unsuitableness of 

 most rocks for their preservation. Evidence, however, 

 so far as we have it, does not show a transition of 

 species into species ; neither can we yet learn much of 

 the Phylogeny of Cicadae from the few fossil larval 

 forms at our disposal ; nor can we yet add much to the 

 interesting question of degradation of organs. 



We have not been able to trace the early simulta- 

 neous rising of brachypterous and macropterous con- 

 ditions of the imagos, as seen in our recent Delphacidae ; 

 for the number of larval examples at our disposal are too 

 few for us to argue, from their absence, that degradation 

 had not commenced. However, Mr. Scudder has re- 

 cently pointed out that such a process of abortion, in the 

 fore-legs of some genera of fossil butterflies, was in 

 operation in early times. 



Although Cercopidas were very common and of large 

 proportions, we are ignorant if they then practised the 

 singular habit of secreting and hiding themselves in 

 spume. Such testimony from the rocks of this mode 

 of concealment would have been of high import, as 

 bearing on the question of acquired habits and here- 

 ditary tendencies. 



