Amphibolips confluenta
James Solomon, USDA Forest Service
Oak Apple Gall Wasps are
usually identified by their gall. This very large gall grows
up to two inches wide, but is usually golf-ball sized. Apple
galls have a thin, papery shell and are spongy inside. They
are green at first, turning brown later. Oak Apple Galls are found
anywhere there are oak trees. Copyright, NC State
College of Agriculture and Life Sciences
The life cycle of this insect is very interesting, although scientists are still learning about it. Adult wasps hatch from galls in June and July. Males and females mate and then drop to the ground. Female wasps burrow into the soil at the base of the tree and inject eggs into the roots.
University of Minnesota
Wasp larvae hatch and munch on the roots for over a year before becoming pupae (resting stage). Only wingless female wasps hatch from the pupae underground. These females crawl out of the soil and up the tree trunk in early Spring. They find a newly-growing leaf and inject an egg into the mid-rib (center vein).
The larvae that hatch inside the leaf are small and round. As they grow, they cause a chemical reaction inside the leaf that forms a gall around the larvae. The gall itself is actually a mutated leaf. Each larva continues eating and growing, and the apple gall grows with it. Apple galls get their name because large galls look a little bit like apples.
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Copyright, NC State College of Agriculture and Life Sciences |
Each apple gall only has one larva inside. When the larva is full-grown, it pupates (resting stage) and comes out as an adult wasp. These adult wasps have wings, are small and dark, and can be either male or female. After drilling its way out of the gall by making a hole, each wasp finds a mate and starts the cycle again. Oak Apple Gall Wasps only lay their eggs in the leaves of oak trees, especially Black Oak, Scarlet Oak, and Red Oaks. Apple galls can be homes to parasites, inquilines, and other organisms. An inquiline is an animal, or other organism, which uses the gall for shelter, but does not hurt the wasp larva inside. Parasites may injure or kill the wasp larva. In Winter, when leaves have fallen, trees can look very strange if they have many apple galls hanging from them. These wasps do not hurt the tree, but heavy infestation (many wasps) can cause leaves to fall early. |
Bruce Kauffman, Tennessee Department of Agriculture
Oak Apple Gall Wasps have many predators, including birds, other insects, Raccoons, and Opossums.
Relationships in Nature:
Southern Red Oak Southern Red Oak Southern Red Oak H
Relationship to Humans:
Oak Apple Gall Wasps cannot sting, so they don't bother people. Since they don't really bother trees either, galls are just something interesting to learn about.
