Wingspan 7 to 8 mm. A small, but fairly distinctive member of the Bucculatrix genus, with its general dark colouration with diffuse paler markings, and noticeable whitish eye-caps.  The larva mines the leaves of Oxeye Daisy, making a long thin meandering gallery.  Later instars leave the gallery and feed freely on the leaf.

Several species of fly make gallery mine Ox-eye Daisy leaves - check for fly maggots/puparia 

Adult Leafmine

Backlit photo of mine; note host.

Where Oxeye Daisy is present.

The adults have two generations, flying in April and May and again in late July and August.

The larvae mine the leaves of Oxeye Daisy

It is widely distributed over much of the British Isles, though absent in some places. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as local.

It appears to be uncommon in Leicestershire and Rutland, where there are few records. L&R Moth Group status = D (rare or rarely recorded).

http://www.leafmines.co.uk/html/Lepidoptera/B.nigricomella.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/ditrysia/gracillarioidea/bucculatricidae/bucculatrix/bucculatrix-nigricomella/