

This is an interesting species (or species complex). The southern populations feed on Oak and have a one-year lifecycle. Northern and western populations feed on heather and willow and have a two-year lifecycle. Populations in the English midlands vary between one year and two year cycles.
I did find a few willows in bud-break:

And also a single specimen of Alder:

And with catkins:

One of the groups I'll be studying closely this year is leaf-miners. I've previously tended to be a bit cavalier in my leaf-miner hunting, but this year I'm going to be more organised, with target species and timescales all planned in advance.