Oak Hedgehog Gall: Food and Shelter for Wasp Larvae

More than in past years, I have recently been paying attention to the insect galls that are found on oak leaves in Eliza Howell Park.

There are many kinds, but I have been focusing particularly on one called Hedgehog Gall, found on the midrib (middle leaf vein) of oak leaves.

Oak species are divided into two major groups: red oaks and white oaks. The tiny wasp responsible for the hedgehog gall, known as the “hedgehog gall wasp,” has a distinct preference for white oaks. The gall is much better known than the wasp.

This is on a Chinkapin Oak, one type of white oak.

As leaves are developing in the spring, the wasp lays eggs and stimulates the tree to abnormal growth at the egg site. The gall is a growth produced by the plant, not the wasp, but it provides the seasonal home and the nutrients for the wasp larvae to feed and grow. Each hedgehog gall has a few cells for developing larvae.

Though the galls are often round, they get their name from the shape that is thought to resemble a hedgehog.

These galls can be found on either the top or underside of white oak leaves and have orangish or reddish hairs. They might look soft, but are very firm, providing excellent protection for the wasp larvae.

If I have my identification correct, these are all hedgehog galls.

Since I started looking carefully, I have been finding many other types of galls on oak leaves. The ones represented in this collage are mostly on red oak trees.

An oak leaf gall is an amazing phenomenon. The insect induces the tree to build a “nest” to raise its young. And, as galls rarely do the tree any real harm, the cost to the tree is minimal. Another of Mother Nature’s many ways of living together.

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