SCHIZONEURIN^. 81 



Tnteoductoet. 



The insects comprised in the two following tribal 

 groups have many characters in common. Their wing- 

 neuration, ringed form of antennse, and life-history, 

 seem naturally to separate them from the foregoing 

 Aphidinge. 



As a general rule, these insects either roll the leaves 

 of trees, or build up gall-like structures on their sur- 

 faces, or otherwise by modifications of their foot- 

 stalks, construct habitations for concealment. These 

 masses are often of considerable size, and by their 

 diversity of shape afford material help towards the 

 identification of the species v^diich make them. 



C. J. Geoffrey seems to have been the first author 

 who drew attention to such galls. In 1724 he com- 

 pared examples, and described them as tenanted by 

 thousands of pucerons. 



Subsequently Reaumur figured roughly, but with 

 considerable spirit, several kinds of these galls. He 

 says of those on the elm tree : — " Il-y-a des annees oil 

 elles deviennent communement plus grosses que des 

 noix, et oil on troifve de monstreuses qui approchent 

 de la grosseur du poing." He says that each of these 

 constructions is the work of one single Aphis, which 

 becomes encircled by the " bottle-like " walls of veget- 

 able growth. 



Von Gleichen also commented on these pseudo- 

 galls, and later Haliday, in the ' Ann. Nat. Hist.' for 

 November, 1838, made some interesting observations 

 on the habits of certain species which he comprised 

 in his new genus Eriosoma. The majority of those 

 named by him are gall-makers. A very similar arrange- 

 ment was proposed by Leach. It corresponds with 

 Latreille's third group of Aphides, amongst which De 

 Geer figured Aphis gallarum iihni, A. tremulce, A. 

 xylostei, and less correctly placed, Aphis gall arum 

 ahietis, which is more nearly allied to Coccus, and is 

 now known as Ghermes ahietis. 



