112 BEITISII APHIDES, 



PEMPHIGIN^. 



The habits of this Tribe are very similar to those of 

 the preceding ; that is, they are gall-constructing, 

 and in some instances they are partly subterranean. 

 Although the known species are not very numerous, a 

 considerable literature exists on the group, which is 

 chiefly of modern date. This attention bestowed is 

 partly due to the obvious distortions produced by these 

 insects on the leaves, or their foot-stalks, of various 

 trees. These curious excrescences and abnormal 

 growths take a great variety of form, and to a certain 

 extent show sach individual characters as materially 

 assist in identifying the species which construct them. 

 The characters of some species are not very sharply 

 defined, and they would not be very easy to identify 

 if the life-history and various methods of building 

 their habitations were ignored. 



