SPANGLE-GALLS. 117 
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 con- 
tains 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 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 fitteen hundred. 
No one who is accustomed to notice the objects which 
immediately 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 vegetable agency. That their substance was 
vegetable was a fact easily settled, but some botanists 
