Chapter XIX. 



Structures of Gall-Flies and Apliidcs. 



Many of the jirocesses which we have detailed 

 bear some resemblance to our own operations of 

 building with materials cemented together; but we 

 shall now turn our attention to a class of insect- 

 architects, who cannot, so far as we know, be matched 

 in prospective skill, by any of the higher orders of 

 animals. We refer to the numerous family which 

 have received the name of gall-flies, — a family 

 which, as yet is very imperfectly understood, their 

 economy being no less difficult to trace, than their 

 species is to arrange in the established systems of 

 classification. 



One of the most simple and very common in- 



Small hcrry-shapcd galls oj" the oah leu/, produced hy Cynipi Quercus yolii ? 



