SPANGUE-GALLS. 493 



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

 the galls are often foimd 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, aa metallic spangles. 



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

 knew precisely whether their growth was due to animal or vege- 

 table agency. That their substance was vegetable was a fact 

 easily settled, but some botanists thought that they were merely 

 a kind of fungus or lichen, while others supposed that they were 

 the work of some parasitic insect. 



When closely examined, these " spangles " are seen to be discs, 

 very nearly but not quite flat, fastened to the leaf by a very small 

 and short central footstalk. Eeaumur set at rest the question of 

 their origin by discovering beneath each of them the larva of some 

 minute insect, but he could not ascertain the insect into which 

 the larva would in process of time be developed. The task of 

 rearing the perfect insect &om the gall is exceedingly difficult, 

 the minuteness of the species and the peculiar manner in which 

 the development takes place, being two obstacle which require 

 a vast expenditure of care and patience before they can be 

 overcome. 



Supposing a branch containing a number of infested leaves to 

 be placed in water and surrounded with gauze, it will die in a 

 week or two, and yet there will be no sign of an insect. If the 

 branch be kept until the winter has fully set in, the desired 

 insects will still be absent, and the experimenter will probably 

 think that his trouble has been thrown away. The real fact is, 

 that the little insects are not developed until the spring of the 



