Hedgehog gall, caused by a tiny cynipid wasp, Acraspis erinacei, on leaves of White Oak (Quercus alba) in Green-Wood Cemetery.
There are three to five larval cells in each of these galls. Only female adults will emerge from these in the late fall, and lay eggs (without mating) on leaf buds. These eggs over-winter, hatching in early spring. The resulting larvae will then develop in other galls, and emerge as adults of both sexes, who mate. Mated females then lay eggs on leaves. When these eggs hatch, they stimulate (annoy?) the tree to form these furry galls, which protect the larvae.
Before he got bogged down the relatively simple complexities of human sexuality, Alfred Kinsey was a cynipid wasp expert. There are thousands of gall-forcing organisms, wasps, mites, fungi. Oak species are associated with hundreds of them.
Hedgehog Gall
Published August 28, 2012 Fieldnotes 7 CommentsTags: Brooklyn, galls, Green-Wood, insects
7 Responses to “Hedgehog Gall”
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Backyard and Beyond 
Cool! I’ve never seen these.
I’ve got these!! How do I get rid of them or do I even need to worry about them??
Most galls are mostly harmless. Commercial tree/fruit growers may differ in their opinion regarding some galls, but for the rest of us, we shouldn’t worry. Indeed, keeping away from pesticides and the like should encourage more insect (there are parasites on gall wasps…) and other life-forms.
Here’s UNL’s take on this particular gall: “Hedgehog gall wasps are dependent upon their host tree for survival so cause, at most, minor damage” http://entomology.unl.edu/scilit/K%20Larsen%20Hedgehog%20Gall%20Wasp.pdf