Wool Sower Gall Wasp - Callirhytis seminator

Several weeks ago my neighbor showed me these interesting growths on one of his white oak trees.

I thought it probably was some type of gall so after a few minutes research I found that it was a gall produced by a small wasp called a wool sower gall wasp, Callirhytis seminator, which only makes its galls on white oak trees. The female wasp lays her eggs in the plant and after hatching, the grubb induces the gall formation.

In the center of these galls are tiny seed-like structures, which is why this type of gall is sometimes also called an oak seed gall. Each one contains a larva which is protected and nourished by the tree.

I cut of a few of the galls from the tree and brought kept them in my garage. After about 2 weeks they had all made their way out of the gall leaving these neat little holes in the side of the galls.

Here are some close-ups of the tiny wasps.

For More information:
Galls on Oaks - NC State University
Springfield Plateau Wool-sower Gall
Wikipedia - Gall Wasp

And don't forget to check out Friday Ark #340!