Swarming Chironomid Midges
These tiny flies can make an autumn afternoon hike interesting when you have to walk through a swarm of them. Fortunately, even though they look like mosquitoes, they do not bite! They are often seen near rivers and slow-moving creeks. I photographed this swarm next to the river below Norris Dam. The swarms are made up mostly of males listening for the frequency of a female's wingbeats. Mated females lay their eggs in water. I often find the tiny worm-like larvae in pond and lake water when I teach my microscope class.
See next photo for a larger swarm.