on underside of Quercus rober leaves
No interactions present.
Yes, these are the spangle galls of Neuroterus quercusbaccarum (agamic generation).
Although widespread and common, and often extremely abundant, the appearance of these galls can be very variable with low numbers in some years, or in some places.
Lat/Lng: 52.4, 1.5
OS grid ref: TM4390