The larvae of the fly Phytomyza tetrasticha mine the leaves of mint, especially Water Mint. The mine starts with a small spiral and then develops into a greenish blotch (frequently on the leaf margin), which turns brown as it ages. The pupa is yellow-brown in the summer generation and deep black in the winter one.

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

The leafmines of Phytomyza obscura and Phytomyza origani are identical those of Phytomyza tetrasticha so the adult must be reared and identified to confirm the species.

ref.: Warrington, B.P. (2023).  Phytomyza tetrasticha. Accessed at https://agromyzidae.co.uk/species/agromyzidae/phytomyzinae/phytomyza/ph… on 13/12/2023)

Leafmine   Adult

Adult: Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

Leafmine: The adult must be reared and identified to confirm the species.

Hos plants: Mint, especially Water Mint.

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.

Leafmines of this species may be found from April to October.

It may pupate either in or outside the mine.

In Britain this species is classed as Nationally Scarce B.

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

Status in Leicestershire and Rutland not known.