OAK-APPLES. 301 



still in the larval state, burrows into the earth, and there 

 changes into the pupal and perfect forms. 



To the unassisted eye, the insect which forms the leaf-gail 

 presents no especial attraction, as it is simply, to all appearance, 

 a little black fly. When placed under the microscope, however, 

 it soon proves to be a really beautiful creature, though not pos- 

 sessing the brilliant and gem-like hues which distinguish many 

 of its relatives. The body still retains its blackness, but has a 

 soft tint on account of the white and shining hairs with which 

 it is thickly studded. The eyes are large, stand boldly from 

 the head, and the many lenses of which these organs are com- 

 posed are so boldly defined, that even in so small an insect 

 they can be distinguished with a very low power of the micro- 

 scope. Indeed, the inch-and-a-half object glass is quite 

 powerful enough to define them, while the half-inch glass makes 

 them look like the pits in a lady's thimble. 



The chief beauty of the insect, however, lies in the wings, 

 which are very large in proportion to the size of the owner, are 

 traversed by a few, but strong nervures, and glow with a 

 changeful radiant lustre, like mother-of-pearl illuminated with 

 living light. In order to see these wings properly, the insect 

 should be laid on some black substance, and the light concen- 

 trated upon them by the various means which a microscopist 

 can always employ. 



The oak is a tree that seems to be especially loved by gall- 

 msects, which deposit their eggs in its leaves, its twigs, its 

 flowers, and even in its roots. One of the most familiar 

 examples of oak galls is that which is called the oak-apple, and 

 which is produced by a species of insect called Cytiips tertni- 

 nalis. Although the insect is not of very great size, the gall 

 which it produces is sometimes enormous, being as large as a 

 common golden pippin or nonpareil apple, and therefore very 

 conspicuous upon the tree. It is coloured in the same manner 

 as the cherry-gall, but seldom sc brilliantly, and the exterior is 

 not so smooth and polished. 



