Andricus paradoxus f. agamic

The asexual generation galls are formed on oak buds from the previous year.  The remains of bud scales at the base, but these may wear off.   Longer than wide, acorn- or egg-shaped, up to 8mm long, and with a blunt tip.  Green and smooth at first with paler spots and streaks, becoming purplish-brown.  Mature galls brown and ridged lengthwise.   There is a single gall-wasp larval chamber, but multiple chambers are made by inquilines. 

Photographs of the gall on the oak twig

oak trees

May to June

uncommon (British Plant Galls, Redfern & Shirley, 2023)

Rare/under-recorded

see species page on Bladmineerders