Amphibolips confluenta (agamic)

Callirhytis seminator (sexgen)

Cynips confluentus

The largest galls in this country [Massachusetts] are commonly called oak-apples. They grow on the leaves of the red oak, are round and smooth, and measure from an inch and a half to two inches in diameter. This kind of gall is green and somewhat pulpy at first, but, when ripe, it consists of a thin and brittle shell, of a dirty drab color, enclosing a quantity of brown spongy matter, in the middle of which is a woody kernel about as big as a pea. A single grub lives in the kernel, becomes a chrysalis in the autumn, when the oak-apple falls from the tree, changes to a fly in the spring, and makes its escape out of a small round hole which it gnaws through the kernel and shell. This is probably the usual course, but I have known this gall-fly to come out in October. 


Cynips seminator

One of our smallest gall-flies may be called Cynips seminator, or the sower. She lays a great number of eggs in a ring-like cluster around the small twigs of the white oak, and her punctures are followed by the growth of a rough or shaggy reddish gall, as large sometimes as a walnut. When this is ripe, it is like brittle sponge in texture, and contains numerous little seed-like bodies, adhering by one end around the sides of the central twig. These seeming seeds have a thin and tough hull, of a yellowish white color; they are egg-shaped, pointed at one end, and are nearly one eighth of an inch long. The gall-insects live singly, and undergo their transformations, within these seeds ; after which, in order to come out, they gnaw a small hole in the hull, and then easily work their way through the spongy ball wherein they are lodged. 

A Report on the Insects of Massachusetts, Injurious to Vegetation