Hedgehog Gall Wasp (Acraspis erinacei)

March 10^th. I was sitting on the ground at the Oconee Heritage Park, photographing some fungi when something caught my eye.

Several of the leaves – White Oak (Quercus alba) leaves – had small ‘furry’ galls on them.

They were approximately 0.5 inches long, and located the central vein on the undersides of the leaves.

A little bit of research identified them as belonging to the Hedgehog Gall wasp (Acraspis erinacei). This wasp has an interesting life cycle. 

Males and females mate in the spring, and the female lays eggs on various white oak species. The hatching eggs irritate cells on the tree, which forms a gall that protects the as many as five larval cells. The larvae feed and mature in the gall, which becomes the distinctive hedgehog gall. The gall is covered with red hairs when young and ages to the brown gall that I found.

Only female wasps emerge from the galls in the fall and, without mating, lay eggs in the buds. The eggs overwinter and hatch in the spring. The larvae develop in a thin-walled ‘blister’ on the inner face of a bud scale appears when the buds open in the spring. Male and female wasps emerge from this gall, mate, and produce the eggs to complete the life cycle. 

References:

- Bug Guide: Acraspis erinacei - Hedgehog Gall Wasp 

- MO Bugs: Hedgehog Gall 

- Backyard and Beyond: Hedgehog Gall