Wingspan 5 to 6 mm. The adults have plain dark forewings with a hint of purple, and an orange head.

The leafmine occurs commonly on Hawthorn, and also on Apple, Rowan and Pear and some other species of Rosaceae.  It has coiled frass and the larva is bright green with a pale brown head (re. Smart, 2018)

The mines are very similar to Stigmella crataegella, but this appears earlier in the year

Adult Leafmine

Check the appearance of the larva and the timing of fresh tenanted mines; S oxyacanthella is later in the year.  Old vacated mines cannot be determined.

In areas where the larval foodplants occur.

A single generation species with adults flying in June. The larva mines leaves in September and October.

The larvae mine the leaves of Hawthorn, Apple and one or two other species. The mine is initially narrow with linear frass, but becomes wide with reddish frass in neat arcs.

It is common throughout much of the British Isles. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as common.

Occasional, though possibly under recorded in Leicestershire and Rutland..

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

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