@adamcotton thank you for the useful suggestions. I provide some more details.

The specimen is a leafminer (found in chard) and it was collected in a field in central Italy (Senigallia), at 500 metres from the sea. The size is less than 2 mm.

Other attachments...

Dears,

I kindly ask for the identification at the level of family (or possibly a finer identification) (see attached pictures).
We excluded Lonchaeidae and we are now evaluating the Chloropidae or Ephydridae.
Thank you.
Best,
Giorgio