DESCRIPTION: A wasp is responsible for the chemically induced distortion of the growing acorn cups on oak trees. The spiky growths, that are a reaction to the egg laying wasp, start green before turning red then brown. This is the agamic stage, the sexual stage is seen as rounded growths on catkins. DISTRIBUTION: Arrived in the UK in 2000 and slowly spreading Northwards. HABITAT: In and around various Oaks.