Oak Knopper Gall

Knopper Galls develop as a chemically induced distortions of growing acorns on English Oak, Quercus robur, caused by the gall wasp Andricus quercuscaliciswhich lays eggs within buds. Andricus quercuscalicis became established in the UK during the 1970s and is now widespread. 
 
Go LARGE.