Species Spotlight: Lake Flies!
It’s May in the Winnebago area, which means everyone’s favorite mother’s day tradition is back: Lake Flies (Chironomids)! These non-biting midges typically hatch around Mother’s Day in late May, though this time frame can shift depending on winter conditions. A second, smaller hatch of lake flies often occurs in late summer.
Lake flies seen around Lake Winnebago are a collection of different midge species, the most numerous likely Chironomus plumosus, also known as the buzzer midge. During the large May hatch, you can easily tell how this species got their common name – there is a low hum from the sheer number of the midges.
Alexsuchy - CC BY-SA 4.0
These flies have wing lengths around 6 mm, and bodies as long as 13 mm. When they emerge to create mating swarms, adults live for only 3 – 11 days. Since they do not have functional mouthparts, they do not bite or even eat! The location and size of swarms are highly dependent on the wind, and are often concentrated on areas that contrast with the background. Females lay masses of eggs on the water surface, which then absorb water and sink to the lake bottom. These eggs hatch shortly after and become midge larvae. The larvae undergo 4 stages, the first of which is free swimming. During the following three stages, the larvae make and live in a tube, collecting food at the bottom of the lake. Then the lake flies emerge in May or late summer and start the cycle over again.
Many species eat lake fly larvae and adults are therefore very important for the food web in Lake Winnebago. In fact, lake fly larvae help support the sturgeon population and contribute to our large self-sustaining lake sturgeon population. Other fish species eat the larvae stages and birds including purple martins and warblers eat the flying adults. Though the large hatching event can be a nuisance for us, they are critical for the food webs of the Winnebago Lakes. Remember, though they can be very annoying, they only last about 2 weeks! Their impact on the rest of the system lasts for much longer.
Article written by Katie Reed, Winnebago Waterways Coordinator: katherine@fwwa.org
Featured Image Credit: Janet Graham CC BY 2.0
Additional Image Credit: Alexsuchy CC BY-SA 4.0
Sources:
Spatial Distribution of Benthic Invertebrates in Lake Winnebago, Wisconsin – Courtney Heling
2022 Chironomid Assessment Report – Lake Winnebago and Upriver Lakes, Winnebago County – WDNR
The Biology of Chironomus plumosus (Diptera: Chironomidae) in Lake Winnebago, Wisconsin – William Hilsenhoff
Lake Bottom Mysteries by Sandy Wickman and Jeffrey Dimick – Lake Tides Volume 40, No. 1, Winter/Spring 2015
Winnebago Waterways is a Fox-Wolf Watershed Alliance recovery initiative. Contact us at wwinfo@fwwa.org
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