Silk-Button Spangle Galls on underside of Quercus robur leaves caused by gall wasp
Silk-Button Spangle Galls seen in late summer or early autumn on the underside of oak leaves. They are caused by the gall wasp Neuroterus numismalis. There is no mark on the top of the leaf, and the gall holds an agamic (ie occurring or reproducing without fertilization) generation of the wasps. The wasp larva inside will mature in August but remain in the gall on the ground (after the leaves have fallen) throughout the winter, emerging the following year from February to April. Neuroterus numismalis gall wasp has two generations per year. One being sexual and the other agamic. The sexual generation causes Blister Galls on Oak leaves the agamic generation causes Silk Button Galls on the underside of Oak leaves.
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Photo credit: © Yon Marsh Natural History / Alamy / Afripics
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