I think that this is a horsefly, a species notorious for making a ragged wound, unlike the deft syringe of a mosquito, so that infection can follow. I have never suffered from this - as opposed to the utter evil of the diminutive Blandford Fly - but then again, I've never seen a horsefly this big. I'm sorry not to have put in my usual fingertip for scale, but I didn't dare put a finger within biting range. The micro moth may help or the eggbox mould. Anyway, it was BIG.