The larvae of the sawfly Profenusa pygmaea mine the upper surface of the leaves of various species of oak creating a large blister mine - usually with a narrow 'neck' where it begins, but without a real initial corridor. Frass in gradually larger grains scattered in the mine.
Leafmine occurs on Oak. http://www.leafmines.co.uk/html/Hymenoptera/P.pygmaea.htm
The mines may be found wherever the host oak species occur
The mines may be found when the host oak species are in leaf.
Never more than one larva in a mine. Pupation outside the mine.
Seems to be fairly widespread in Britain.
Status in Leicestershire and Rutland not known.
Leicestershire & Rutland Map
Enter a town or village to see local records
Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015