Oak artichoke galls

This gall is made by the parthenogenetic Cynipid gall wasp Andricus ffoecundatrix,
which lays single eggs within leaf buds using their ovipositor and produce a
chemically induced distortion of leaf axillary or terminal buds on Pedunculate Oak (Quercus robur). It can also affect to Sessile Oak (Quercus petraea) trees

The larva lives inside a smaller hard casing inside the artichoke and this is released in autumn. The asexual wasp emerges in spring and lays her eggs in the oak catkins which will cause the formation of the 'hairy catkin galls', small oval galls which produce the sexual generation of wasps.

A well grown specimen can be 2.0 cm long, dark green or russet, generally developing in June and reaching its full size before autumn.