Spangle galls on the underside of leaves of pedunculate oak, Quercus robur. The picture, taken in late Summer, shows galls of two species of the cynipid gall wasp Neuroterus. The more numerous are common spangle galls, produced by N. quercusbaccarum (flat, spotted circles). Above centre and to right, are 13 silk button spangles, caused by N. numismalis. A gall is produced when, in early summer, a female wasp lays eggs inside a leaf. The plant reacts by forming a cavity, before the larva hatches. The larva crawls into the cavity and remains there as the spangle develops. In late Autumn the galls fall to the ground. The larva overwinters within the gall and emerges in following Spring