Question about midges.

beveragelady

What do they eat when I'm not there?
We camped a couple of days ago at a lovely secret spot in the Slieve Blooms. We've never really had a midge problem there before but the conditions were perfect for the midgepocalypse. We had sprays and cream and net hats and everything but they got my ankles and muffin-top area as usual. There is a stream, there are trees nearby and there is tall grass, it's exactly the sort of place where you know you'll find midges. There were millions of them and they made their way into the tent on our clothes, on the dogs and by teleporting through the groundsheet.
So I found myself wondering... what do they usually bite? Surely they don't hang out there on the off-chance I'm going to wander along with skin exposed? It's half a km at the very least to the nearest livestock. Is there enough wildlife on that stretch of river to support that kind of midge population?