Wingspan 9 to 10 mm. One of the larger species of Phyllonorycter, with a rather attractive 'striped' appearance, each stripe gradually fading from whitish through chestnut to black. The larva mines the leaves of Alder, creating a large under-surface tentiform without clear folds. The mine is between two veins and often stretches from midrib almost to leaf-edge.  The mature larva is greyish, and pupates in a frass-free cocoon in the mine.  

Mines can be similar to P rajella or P klemannella; if in doubt, larvae and pupae should be examined.(ref: Bladmineerders.nl)

Adult Leafmine

Photograph undersurface of mine, and larva or pupal cremaster; note host species

Areas where Alder is present.

The moth is believed to have only a single generation, flying in July and August, though bred specimens will emerge in spring if kept indoors. 

The larvae feed on Alder, and create a long mine between two veins on the underside of the leaf. Often there are several to a leaf.

Widespread and common in Britain. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as common.

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/P.froelichiella.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/ditrysia/gracillarioidea/gracillariidae/lithocolletinae/phyllonorycter/phyllonorycter-froelichiella/