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Photo#357564
Wool sower gall on Quercus alba: Callirhytis seminator - Callirhytis seminator

Wool sower gall on Quercus alba: Callirhytis seminator - Callirhytis seminator
Raleigh, near Rts 50 and US 70. Lake Lynn City Park., Wake County, North Carolina, USA
April 20, 2007
Size: Baseball
Several of these galls on young white oak trees near each other. Older trees were just getting new leaves. I read that this is the "leaf gall" of the wasp. It appeared to be around a young branch.

"leaf gall"
These galls are always attached to twigs, as you observed. I think the term "leaf gall" must refer to the fact that this is a spring gall--the gall that produces the sexual generation, which tends to be a succulent gall on a bud, flower, or leaf--as opposed to the autumnal gall, which produces parthenogenetic females (many of these are twig galls, but there are plenty that are leaf galls, acorn galls, etc.). Why someone would choose to call it a "leaf gall" rather than a "spring gall" is a mystery to me.