Wingspan 4 to 5 mm.  The larva mines the leaves of various smooth leaved willows - e.g. Crack Willow and Weeping Willow. causing an angular gallery mine

Adult Leafmine

Photogrpah mine with backlight, and note host species (or group - e.g. 'a Wiilow')

Where smooth-leaved willows occur.

The adult moths emerge in two generations: in May and August.

The eggs of this species are laid on either side of the leaves of one of the smooth-leaved willows. The yellow larvae emerge in June and September and create a narrow mine, often parallel to the rib of the leaf.

The moth is widely distributed, but not particularly common in most of Britain. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as local.

Occasional in Leicestershire and Rutland but increasingly well recorded from the leafmines on smooth-leaved willows such as Crack-willow, White Willow and Weeping Willow.

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

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