Larvae of the gall midge Macrodiplosis roboris cause the leaves of Oak to roll upwards forming a gall. The rolls usually occur between the lobes of the leaf.  An orange larva is inside the gall

Macrodiplosis pustularis causes the lobes of oak leaves to fold down 

Gall  Adult

Areas where Oak is present.

Fresh galls can be encountered from June until late September when the rolls turn brown and the larvae escape.

Larvae white at first, ± orange later; one generation per year; the larvae hibernate in the soil.

Probably fairly frequent in Britain, but status is difficult to determine due to lack of records.

Status in Leicestershire and Rutland not known.