I have been finding leaf-mines of a moth which has very few (if any) records around this area and has generally been considered scarce in, I think, the whole of Britain. But I have encountered reports of its increase and that might well be the case. Part of the problem might be that they are not very visible being, as they are, in hairy leaves of White and Grey Poplar. I've found them in Herts, Middlesex (Regent's Park, no less) and eventually in Bucks - just outside Denham Garden Village.
Unlike most Phyllonorycter, P. comparella emerges now and hibernates. The remains of the chrysalis is visible, poking out of the membrane of the mine: