The agamic (asexual) generation causes galls in the axillary leaf bud of various Oak species.  The pear-shaped gall is about half a centimetre high and covered in silky white adpressed hairs that point downwards. Inside the tip is an inner gall containing the larval chamber.  It is mainly seen on young shoots.

In the BPGS key (Redfern & Shirley) the gall is described as generally reddish, or purple, and the hairs may be violet coloured.  All galls photographed in VC55 so far are green with white hairs. 

[Note: The sexual generation forms galls on catkins, and is rarely recorded.] 

Several other gall-wasps form galls in oak buds and catlkins.

Photograph the gall on oak, and note the host species

native oak trees. In VC55 it seems to be associated with old woodlands

Locally common (British Plant Galls, Redfern & Shirley, 2023)

probably under-recorded, but may be quite common locally

See British Plant Galls (Redfern & Shirley, 2023)