Found these all over the leaves on a sycamore was wondering if they are a gall.
No interactions present.
Similar galls also found on Alder leaves. Not sure if same mite causes them.
There are a number of organisms that produce raised galls on Alder leaves. Aceria cephaloneus is restricted to Sycamore.
Your ID is correct but the name is now cephalonea.
Lat/Lng: 50.639, -3.3096
OS grid ref: SY074829