Spongy Oak Apple Gall - Amphibolips confluenta
I found several of these galls on this tree, but this one appeared deformed. I opened it up and it was full of frass. I wonder if it was parasitized.
Galls are green at first, but become tan and papery thin on the outside as seen in this photo. The gall was about 4 cm diameter.
Habitat: Spotted on an oak tree in a deciduous forest.