Mayfly

Welcome to Michigan mayfly season

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Around the start of each June, thousands of winged wonders take to the skies from the banks of Lake Erie. It’s not birds we’re talking about, but the Giant Michigan Mayfly (Hexagenia limbata)! These creatures spend one to two years living burrowed in the mud on the lake’s floor, hatching to its second stage as a winged bug only after spending the necessary time to grow. Mayflies tend to disperse everywhere among the four states touching Lake Erie, and they’re more important to the Great Lakes than you may realize.

DTE Energy noticed the annual phenomenon at our Fermi 2 plant. So, we spoke with Patrick McCafferty, a retired entomology professor from Purdue University, where he founded and is the chief contributor to Mayfly Central. The website is part of the university’s program to engage students, fly-fishers, naturalists, agencies and environmental workers in the issues surrounding the species’ delicate ecosystem. From him, we learned that even in the insect’s shockingly short lifespan – usually between 24 and 72 hours – they manage to leave their own positive imprint on our ecosystem.

McCafferty shared that mayflies are an important cog in the freshwater environment because they consume detritus and algae. (Algae blooms use up available oxygen that other lake organisms need, and can be toxic to people and wildlife alike.) The mayflies are also a food source for fish and birds at both stages of their evolution. For these reasons, we should not be attempting to limit their populations—Erie has made a promising recovery to some extent, partly thanks to these critters.

Mayflies are also known as an “indicator species,” because the size and health of the swarms tell scientists the current health of Lake Erie. In their nymph stage underwater, they are quite vulnerable to silt and pollution. They are even more interesting to researchers in that they are one of the geologically oldest of all winged types of insects. Fishermen have also been using them as bait for decades!

In terms of reducing the nuisance to our homes and communities. McCafferty says the best thing to do is to not attract them with lights at night. Most white lights (e.g., incandescent, florescent, mercury vapor) are attractive, so the so-called yellow “bug lights” are much preferred if you’re able to find them. Otherwise, let them do their amazing work for our environment!

Curious as to how fire also plays a positive role in our native habitats? We have the scoop →