The mite Aceria macrorhyncha causes a red pouch gall on the upper surface of Sycamore leaves.  When fully developed in late summer, the galls are up to 6mm high, with a pointed apex.

Aceria cephalonea also cause galls on Sycamore; these are smaller when fully developed, with a rounded apex.

Gall Adult

Some indication of the size of the gall is needed.  The host plant must be specified in the comments box - e.g. "Galls on Sycamore, 5-6mm high".   In Spring and early Summer, before fully developed, these galls may be indistinguishable from Aceria cephalonea and should therefore be recorded as the species aggregate Aceria cephalonea agg. 

Wherever Sycamore is found.

Summer and Autumn.

Quite common and widespread in Britain.

Fairly common in Leicestershire and Rutland.

See Buckton, S.J (2023) Lessons from verifying Yorkshire galls and gall-causers on iRecord  Cecidology 37 (1) 28-40