Flip Side Of An Oak Leaf
Caused by a Gall wasp
The gall wasp has 2 generations per year. One being sexual and the other agamic (all female, and needs no male to reproduce). The sexual generation causes Blister galls on oak leaves. Whereas the agamic generation causes Silk button galls on the underside of oak leaves. The agamic generation was previously named N. vesicator before it was realized to be two generations of the same species.