An Oak Apple or Oak Gall is another type of Gall cause by a Gall Wasp. I posted a photo of a different type of Gall a few days ago (Gall Caused By A Gall Wasp). That Gall was small and fuzzy. The Oak Apple has a thin, papery shell and are spongy inside. They can be up to two inches wide. They start out green and then turn brown later.
Something I didn’t know until I did some research is that the Oak Apple has been used in the production of ink since at least the time of the Roman Empire. From the Middle Ages to the early twentieth century, iron gall ink was the main medium used for writing in the Western world.
I see several of these while hiking in the Ouachita National Forest here in Arkansas. Most of them are found on the ground this time of year. I tried to find one to photograph hanging from a tree, but I was unable to. I will try to remember to photograph a green one the next time I see one.
Oak Apple Facts
Oak apple or oak gall is the common name for a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 3⁄4 to 2 inches (2 to 5 cm) in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae. The adult female wasp lays single eggs in developing leaf buds. The wasp larvae feed on the gall tissue resulting from their secretions. Considerable confusion exists in the general “literature” between the oak apple and the oak marble gall. The oak marble is frequently called the oak apple due to the superficial resemblance and the preponderance of the oak marble gall in the wild. Other galls found on oak trees include the oak artichoke gall and the acorn cup gall, but each of these has its own distinctive form. (Wikipedia)