Geograph - photograph every grid square

It has been a year with very few galls on the Oaks. This one twig on this one tree is variously infected, but even here the rest of the tree is largely unaffected.

On the left is the flattend disk of the Oak Spangle Gall caused by the asexual generation of a cynipid wasp, Neuroterus quercusbaccarum. On the right are the spherical homes of the bisexual generation of the same wasp, housed in a green Currant Gall, in which it will overwinter. See Link and Link (Archive Link )

In the middle the small mounds with a hollow top are Silk Button Gall - formed by Neuroterus numismalis. Another cynipid wasp, this is also the asexual generation. The bisexual form causes thickening of the leaf, bulging above and below without breaking out. I have never observed this form, perhaps it hides too well. See Link and Link (Archive Link )