Gall wasps Cynipidae are themselves small, inconspicuous and difficult to identify. The larvae have a clever sttategy liveing within galls which they induce on various plants, oak being a great favourite. A common pattern is for an alternation of 2 generation each year, one sexual and one parthenogenic, producing different types of gall (even on different plant species).
Deeply grooved or ridged outgrowth found on Acorns of traditional English oak The Peduculate Oak ( Quercus robor) caused by larvae of tiny gall wasp Andricus quercuscalicis.(Burgsdorf, 1783) Following generation develops in galls induced in Turkey oak catkins. Cycle is then repeated in pendunculate oak. The insect is a recent comtinenetal introduction circ 1962
Gall wasps have complex life cycles with an alternation of a sexual and asexual generation each year. The Females only emerge from the knopper galls and these lay their eggs in the buds of the Turkey Oak (itself an invasive non-native species). (Quercus . cerris). In spring this sexual generation causes minute galls in the male catkins.
A Knpper or Knpp a 'knop' as "a small rounded protuberance, boss, stud, button, tassel similar. Single galls are about 22mm across.