116 SOCIAL HABITATIONS. 
galls were left on the tree. The incipient naturalist 
who made the mistake kept the buds for some eighteen 
months, and was sadly disappointed to find that no 
insects were produced from them. 
The insect whose acrid injection produces this curious 
effect upon the tree is rather larger than the leaf-gall 
insect, and is of more slender proportions. It has been 
suggested that the object of the leafy or hairy covering 
is, that the insect, which remains in the gall throughout 
the winter, should have a warm house by which it may 
be protected from the chilling frost as well as from the 
wind and rain. 
If the reader will again refer to the illustration, he 
will see that from the same branch on which the Cynips 
Kollari has formed so many galls, depend two slender 
threads supporting one or two globular objects. These 
are popularly called CURRANT-GALLS, because they look 
very much like bunches of currants from which the 
greater part of the fruit has been removed. Their colour, 
too, is another reason for giving them this name, as they 
are sometimes scarlet, resembling red currants, and some- 
times pale cream colour, thus imitating the white variety. 
These galls are placed upon the catkins of the oak, 
which are forced to give all their juices to the increase 
of the gall, instead of employing them on their own 
development. Some authors think that the insect which 
forms them is a distinct 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, 
