The larva mine the leaves of willows such as Crack-willow and Osier producing an elongated yellowish blotch mine.

See the National Agromyzidae Recording Scheme webpage for this species for further details of puparium and adult insect .

ref.: Warrington, B.P. (2023).  Aulagromyza tridentata. Accessed at https://agromyzidae.co.uk/species/agromyzidae/phytomyzinae/aulagromyza/aulagromyza-tridentata/ on 12/12/2023)

The larvae of the micro-moth Stigmella obliquella and the weevil Isochnus also cause leaf-mines in narrow-leaved willows.

Leaf-mine Adult

Provide backlit photographs of the whole leaf-mine in the leaf, and the larva, and note the host plant. It may be necessary to rear the adult insect to confirm identification. 

Where willow, the larval foodplant is present.

Click on the 'further details' link in the 'Description' section above.  Then click on the Phenology tab which will provide phenology details for both adult and larval stages.

The larval leaf-mines may be found between July and November.

Larvae feed on Crack willow, Osier and other willows.

Nationally Scarce B.

Warrington, B. P. 2022. A provisional review of the status of Agromyzidae in Great Britain & Northern Ireland

Occasional in Leicestershire and Rutland.

http://www.leafmines.co.uk/html/Diptera/A.tridentata.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/diptera/brachycera/agromyzidae/phytomyzinae/aulagromyza/aulagromyza-tridentata/