While clearing up some low hanging limbs on one of our oak trees, I found this under a leaf—an oak apple gall. The gall is created by a tiny wasp of the Cynipidae family that lays its egg in a young oak leaf. The secretions from the egg cause the leaf to mutate and create this structure—humans are not the first to experiment with genetic engineering. If you open the gall up, you will find a small center capsule that holds the larvae and is suspended by filaments stretching out to the thick walls of the gall. The wasp will emerge later in the summer. This gall is about an inch in diameter. Click on the image for a larger view.