The swarms make it easier for the male and female gnats to find each other and mate, Gregory Courtney, an entomology professor at Iowa State University, told Live Science. Gnats will often congregate around objects or other visual markers that contrast the landscape, such as fence posts, Courtney said.

How do you get rid of a swarm of midges?

Create a midge trap

Put apple cider vinegar into a bowl with a few drops of washing up liquid. Midges are attracted to the smell of the mix but get stuck when they land! Don't forget to empty and clean out the bowl, and replace the mixture every few days.

Where do midges congregate?

However, in smaller numbers, midges can be found across most of the country where areas of damp soil for breeding can be found. Midges prefer to lay their eggs in damp, boggy ground, and acidic peat soils in particular.