Wingspan 9 mm. A tiny, but distinctively marked species, with pale yellow shoulder patches and scale tufts along its back.  The larva mines the leaves of Rosebay Willowherb, causing gallery and then blotch mines, often tinged red and yellow.  The larva is yellow.

Bladmineerders.nl lists Mompha langiella as a rare miner of Rosebay Willowherb

Adult Leaf mine

Backlit photograph of mine; note host

It can be found in any habitat where the food plant grows.

It has two generations in the year, flying during May and again in August.

The larvae mine the leaves of Rosebay Willowherb

Fairly frequent and widespread in Britain but easily overlooked due to its tiny size. In the Butterfly Conservation’s Microlepidoptera Report 2011 this species was classified as common.

Occasional in Leicestershire and Rutland. L&R Moth Group status = C (very scarce resident or rare migrant)

http://www.leafmines.co.uk/html/Lepidoptera/M.raschkiella.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/ditrysia/gelechioidea/momphidae/mompha/mompha-raschkiella/