Two Andricus kollari (Hymenoptera: Cynipidae) which emerged from a pair of oak marble galls. These are females of the asexual generation.
I had collected the galls in a small plastic tub which I then left on a desk beside our PC. After a few days I noticed these wasps in the tub. Each wasp had emerged from its own gall, leaving a neat round hole:
I cut one of the galls in half with a hack-saw:
Galls collected in Whiteknights Park, Reading, UK, on 2014-08-17, wasps emerged on 2014-08-22.