Knopper gall on acorn

Description:

The Latin name is of the tiny wasp that causes the gall to grow. I couldn't find a Latin name for the gall itself.

Habitat:

On an oak tree in a deciduous woodland.

Notes:

The wrinkly mutant acorns are known as Knopper Galls and are made by the Gall Wasp, Andricus quercuscalicis, which looks like a tiny black fly just a few millimetres long. Earlier in the summer, the females of this species laid eggs on the buds of developing acorns and a fascinating transformation was triggered as soon as they hatched. Responding to a chemical signal released by the larvae, the oak tree was persuaded to sculpt its tissue into knobbly Knopper Galls in place of normal acorns. When there are just one or two larvae inside, the result is a fairly simple, folded structure but, when several inhabitants are competing for space, the galls look more contorted, like mini explosions frozen in time.