I've got it! Well at least the bathroom floor has got it. Common furniture beetle as far as I can tell. Taken off some panelling, which had seen better days, thats now in the garden. I've not taken up the floor boards yet, but I'm getting a handful of adults coming out every 24hrs or so.
Going to lift the boards tomorrow. Assuming I'm going to find some bathroom generated damp, which I've cured, but not time enough to dry out fully yet. Also assuming I'm going to find it either really bad, in which case will all need replacing, or mild enough so that I can live with the existing damage if I can stop any more.
So the question of the day is, if I've stopped the damp, and the damage isn't too bad, do I dare not to chemically treat it. I think its likely to be fairly localised. And if I do think a dose of something is needed to keep it in check, what is the go to chemistry?
All advice welcome.
Just splashit all over with borax.
They'll either eat it on the way or the way out and you kill em dead.