SPANGLE^GALLS. 307 



species, while others think that the galls are the production of 

 the same insect which forms the leaf-gall, the punctures being 

 made in the stalk of the catkin and not in the nervure of the 

 leaf. 



That this supposition may be correct is evident from the fact 

 that the same insect which forms the oak-apples does also 

 deposit its eggs in the root of the same tree, causing large 

 excrescences to spring therefrom, each excrescence being filled 

 with insects. I have often obtained these root-galls, several of 

 which are now before me, some having been cut open, in order 

 to show the numerous cells with which they are filled, and others 

 left untouched, in order to exhibit the form of the exterior. 

 Being nourished by the juices of the root, they partake of the 

 sombre hues which characterise the part of the tree from which 

 they spring, and do not display any of the colours which are 

 seen on the oak-apples which spring from the twigs. 



There are. however, distinct species of gall insects which 

 pierce the roots of the oak-tree. One of them is termed Cynips 

 aptera^ and makes a pear-shaped gall about one-third of an inch 

 in diameter. Each gall contains a single insect, and a number 

 of the galls are often found attached by their narrow end to the 

 root-twigs of the tree, something like a bunch of nuts on a 

 branch. There is another insect which is termed Cynips quercus- 

 radicis, which forms a many-chambered gall of enormous size, 

 containing a small army of insects. Mr. Westwood mentions 

 that one of these galls in his possession was five inches long, 

 one inch and a quarter wide, and produced eleven hundred 

 insects, so that the entire number was probably fourteen or 

 fifteen hundred. 



No one who is accustomed to notice the objects which imme- 

 diately surround him can have failed to observe the curious 

 little galls which stud the leaves of several trees, and which 

 are appropriately called Spangle-galls, because they are as 

 circular, and nearly as flat, as metallic spangles. 



These objects had been observed for many years, but no one 

 knew precisely whether their growth was due to animal or vege 



