Adult Stigmella are very difficult to identify and this species is best recorded as a leafmine on Rowan

The mine is a long narrow gallery, often contorted, with a thin central line of linear frass.

The mine can be very similar to those of Stigmella nylandriella, but this has coiled frass

Adult Leafmine

Adult: It may not be possible to identify adult Stigmella even by dissection unless reared from the leafmine.

Leafmine: May be identifiable with care, with provide good photographs including a backlit image. Please also state the host species (i.e. usually Rowan). 

Areas where Rowan occurs.

The leafmines may be found from late June to August and persist until the leaves fall.

Larva mines the leaves of Rowan (Sorbus aucuparia)

Mainly found in the north and west of Britain. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as local.

Rarely recorded in Leicestershire and Rutland.

http://www.leafmines.co.uk/html/Lepidoptera/S.magdalenae.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/monotrysia/nepticuloidea/nepticulidae/stigmella/stigmella-magdalenae/