Wingspan 10-13 mm. This is another distinctive Caloptilia. Although quite variable, this is the best marked of the group. The larva mines the leaves of Lilac, Ash, Privet and Jasmine, often gregariously, in a large blotch mine.

Adult Leafmine

Photograph leaf mine; note host species

Gardens and woodland.

The adults fly in May and again in July.

The larvae feed on Lilac, Ash, Privet and Jasmine and can be a pest in gardens. Often, many leaves on a single bush turn brown and curl up with the mines.

A common species throughout Britain. They and can be very common indeed where the mines are to be found. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as common.

Now seems to be fairly frequent in Leicestershire and Rutland.

http://www.leafmines.co.uk/html/Lepidoptera/C.syringella.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/ditrysia/gracillarioidea/gracillariidae/gracillariinae/gracillaria/gracillaria-syringella/