This document printed from the University
of Illinois Extension A Gardeners Place at http://www.extension.uiuc.edu/cook/
Gnat Invasion
July 4, 2005
Ron Wolford
Unit Educator, Urban Horticulture and Environment
Cook County Unit 3807 West 111th Street
Chicago, IL 60655
Phone: 773-233-0476
FAX: 773-233-0910 rwolford@uiuc.edu
I was watching the Cubs game Sunday with the sound off and WGN Radio, the Cubs Flagship station, on. As I walked past the TV, I noticed wild hand waving going on in the stands. A close-up by the TV camera showed clouds of gnats had invaded Wrigley Field. According to people attending the game, the gnats were intolerable, buzzing around and getting into food and drink.
The gnats are actually non-biting midge flies. They are also called "blind mosquitoes" because they look like mosquitoes, but they do not bite. Midges are aquatic insects often found in and around urban ponds and lakes like Lake Michigan.
Female gnats lay their eggs on the water's surface. One egg mass can have over 3,000 eggs in it. The eggs will sink to the bottom and larvae hatch in a few days. The larvae make mud tubes to live in for anywhere from 2 to 7 weeks. After the larval stage the pupa forms and swims to the surface and in 3 or 4 hours the adult emerges. This whole process from egg to adult can take as little as three weeks during the warm summer months. Several generations may emerge during the spring and summer months.
So, why did the gnats decide to show up and disrupt the Cubs' game? Well, the most obvious reason is Wrigley Field's close proximity to Lake Michigan and the Chicago River. Another factor is the extended period of wet weather we have been experiencing. But, for the gnat, this swarming behavior is part of their mating process. Because gnats are so small, the males swarm to attract females. After mating the adults live for only three to four days.
Is all the news about gnats bad? Well, fish like them, especially bottom feeding fish like carp and catfish. Midges are a food source for many water organisms including dragonflies.
This swarming behavior actually delayed a game between the Chicago White Sox and the Baltimore Orioles on June 2, 1959 for a half hour. The grounds crew got rid of the gnats using smoke bombs. On September 15, 1946, the game between the Chicago Cubs and the Brooklyn Dodgers at Ebbets Field was postponed after swarms of gnats descended on the field in the fifth inning.
It seems Chicago baseball teams and gnats have a common history, so, the next time you go to a baseball game don't forget to bring along some mosquito netting.
