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CHAPTEK XIX. 



STRUCTURES OF GALL-FLIES AND APHIDES. 



Many of the processes 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 knoAv, be 

 matched in prospective skill bj 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 ; though the latter han 

 been recently much improved by Mr. Westwood. 



Small berry-shaped galls of the oak leaf, produced by Cynijjs queixusfoliir 



One of the most simple and ver}'- common instances of the 

 nests constructed by gall-insects, may be found in abund- 

 ance during the summer, on the leaves of the rose-tree, the 

 oak, the poplar, the willow {Salix viminalis), and many other 

 trees, in the globular form of a berry, about the size of a 



