I found around 15 mines of Ectoedemia argyropeza on fallen Aspen leaves at Hailey Park meadow, Llandaff North, today. This seems to be the first record for VC41. The mines were pretty obvious due to the distinctive green windows they create in the yellowing leaves:
The mine begins in the petiole then moves into the leaf itself. Most of the mines were still occupied despite having fallen from the trees.
Mine in petiole
Larva in mine
There are plenty of Aspens in the meadow at Hailey Park, presumably planted after it was landscaped following closure of the landfill site. Although this tree is generally quite uncommon in South Wales, it is often planted in parks and I'm sure the moth must occur elsewhere. This must be the best time of year to look for them, as the green windows are so obvious.