Oak Apple Gall Wasp

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.

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.

Additional Media

Description
Type
Credit
Unidentified Gall Wasp's Head Under a Microscope
Link to Image
Uglybug.org

Relationships in Nature:

FOOD
PREDATORS
SHELTER
OTHER

Black Oak

Downy Woodpecker

Black Oak

Black Oak H

Southern Red Oak

Carolina Chickadee

Southern Red Oak

Southern Red Oak H

Raccoon

Dogwood Borer SP

Virginia Opossum

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.

SCIENTIFIC CLASSIFICATION

KINGDOM
Animal
PHYLUM
Arthropod
CLASS
Insect
ORDER
Hymenoptera
FAMILY
Cynipidae
GENUS
Amphibolips
SPECIES
Amphibolips confluenta

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