TWO YOUNG NATURALISTS. 261 



way of working is without doubt the Cynips, although 

 it is little known to the ordinary observer. This 

 Hymenopteron is completely associated with the tree, 

 and locates itself thereon at a fixed spot that it has 

 itself selected, and there causes a habitation to grow 

 up in which it establishes its posterity. You have 

 no doubt often noticed on the leaves, along the ribs, 

 or at the base of the stalk, some peculiar objects, 

 some fleshy excrescences, that resemble aborted apples. 

 These are the productions of the Cynips or gall-fly. 

 Its piercing apparatus, by penetrating into the plant, 

 sets up some peculiar affluence of sap, and thus is 

 formed an excrescence that gradually increases in 

 size. In this the offspring is produced, and hidden in 

 it, after the manner of La Fontaine's rat retired from 

 the world in the cheese, it grows up to its full size as 

 a grub or maggot, and comes out in the winged form 

 to carry on the continuance of the species. 



It is to a Cynips of an oak of the forests of the 

 East, the Quercus infectoria, that we owe the gall-nuts 

 whose use is so widely diffused by commerce, and 

 which form one of the ingredients of writing ink ; so 

 that large numbers of people devote their industry to, 

 and obtain the means of existence from, this tiny 

 creature. And, wonderful fact ! this pigmy living on 

 a giant tree has its own pigmies devoted to it ; this 

 guest is itself the host of parasites. The little habita- 

 tion of the Cynips frequently gives shelter to a num- 



