The horror... 
http://www.theatlantic.com/science/archive/2015/09/arctic-mosquitoes-and-the-chaos-of-climate-change/405322/
Arctic Mosquito Swarms Large Enough to Kill a Baby Caribou
I've experienced true killing swarms, in northern Quebec. It wasn't pretty.

When the weather and breeding conditions are "just right" (or "just wrong"), the sheer number of mosquitoes you can get is awe inspiring.
I remember one time I was sitting with my wife on the (screened) porch at the far northern cottage ("cabin" for you Yanks

), in early June, when night started falling. We heard what sounded like a motorboat starting up on the lake nearby and comming close. I shined my flashlight out at the water to see who it was - it wasn't a motor, it was the buzz of literally
millions of mosquitoes swarming the cottage like something out of a horror movie. The screen was solid black with them - you couldn't actually see out.
We had to use a chamber pot that night - I wasn't opening that door for any reason whatsoever.

I can well believe that swarm would, quite literally, kill any animal unable to take cover or swat.