In reply to Trangia:
I don't think either bite is poisonous as such (wasp stings you usually put something acidic on it, even a fruit sweety would do). But you could have a reaction more likely to the first bite which could last 48 hours. Plenty of horse flies in Scotland at present. I'm lucky - they bite me - I kill them, and that's the end of it, apart from an unpleasant feeling about the whole thing.