Mating swarms of non-biting midges drift in the mid-day air on an unusually warm December day in Hartford. River birches
frame the photo. Photo by urbpan
. Location: The Riverwalk, Hartford, Connecticut.
Urban species #347: Non-biting midge Family: Chironomidae
A column of insects gathers in the air, slowly drifting, sometimes toward a light source, sometimes toward an object such as a passing human. The column may be a small vertical puff of a few feet, or a towering nimbus hovering from face level up to thirty feet tall. If you are like me, you swish your hat through the cloud to catch one or two of these tiny flyers, to see what they are. You may be alarmed to see what looks like a mosquito! But if they were all mosquitoes you would be covered with bites by now. Midges can be told from mosquitoes by the lack of scales on their wings, different mouthparts, and by the fact that their front pair of legs is their longest. The cloud moves on, perhaps leaving one or two tiny flies in your hair or, if you were riding through on your bike, your eye.
The insects are midges, specifically "non-biting" or "chironomid" midges. (They are called non-biting midges to distinguish them from small biting flies such as no-see-ums, which are sometimes called midges.) The columns are mating swarms, and the vast majority of the midges in the swarms are the males. Male midges (and males of mosquitoes and moths
) can be recognized by their plumose, or featherlike antennae. These are surface-area maximizing structures which catch scent molecules and draw the males to their purpose.
Midges are almost always found near fresh water, where they live as larvae. Midge larvae are among the most abundant and important aquatic invertebrates. They are food for other insects, as well as young fish
. Astute ecologists can determine a great deal about a body of water by the midges that live in it. Each species can tolerate different levels of different pollutants, as well as different pH levels, temperatures, levels of oxygenation and so on.
Adult midges, though tiny, can be important food for birds and bats
are drawn to bodies of water to catch the adults as soon as they emerge from their aquatic pupae. One imagines that this swarm of midges photographed at the bank of the Connecticut River in December has an adaptive advantage: by engaging in the mating swarm in winter, they have thwarted their bird, bat, and dragonfly
predators, who have migrated or are hibernating.
A male midge swept out of its swarm with my hat.
Thanks for identification help from rockbalancer