Emerging from the deep
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EmailLakes are nurseries for a fascinating variety of insects; did you know that many insects – including dragonflies, mayflies, and mosquitoes – spend the first stages of their lives underwater?
Spend a moment or two along the lakeshore and you’ll notice them. Swooping through the breeze, buzzing in the trees, skimming along the water’s surface – insects! As the sun sets, hundreds of mayflies rise out of the water as if on cue. On a sunny day, a dragonfly might land on the end of your fishing pole, only to zip away again in pursuit of pesky mosquito prey.
Mayflies
Mayflies (insects of the scientific order Ephemeroptera, from Greek words meaning “short-lived” and “wing”) are a familiar sight near many Michigan lakes when they emerge (or “hatch”) from the water as flying adults. Mayfly eggs hatch in or near the water and the aquatic nymphs look like the adults, except for the lack of wings. They live in the water for a few weeks, crawling along the lake bottom or burrowing into the sediment, where they feed on detritus and other insects. When a mayfly nymph is ready to emerge, it uses the water’s surface tension for support and sheds its exoskeleton to emerge as a winged “pre-adult,” or subimago. The subimago flies into the air and lands shortly thereafter to molt a final time to the imago (adult) stage.
The mayfly’s adult lifespan is very brief – often only a single day. During that day, it has one goal – to reproduce. Adult mayflies do not feed; they don’t even have mouths! Because their adult lives are so short, it’s critical that there are mates available. That’s why mayflies seem to emerge as adults all at once, and we see great swarms of them along lakeshores, especially near lights, on late spring and early summer evenings. These emergences can cause feeding frenzies among fish and birds that enjoy feasting on mayflies. You may also observe fishing frenzies among anglers who take advantage of this opportunity to catch hungry fish!
Dragonflies
Dragonflies (of the order Odonata, from the Greek for “tooth”, in reference to their predatory mandibles) have a similar life cycle to that of mayflies. Dragonfly eggs hatch into a wingless aquatic nymph. Dragonfly nymphs, like adults, are predators. They lurk on the lake bottom, waiting for unsuspecting insects to venture close then snap them up with toothy mandibles. When it is time to emerge, the dragonfly nymph will crawl up out of the water on the stem of an aquatic plant like a bulrush or cattail, or on a structure like a dock support, and shed its juvenile skin and emerge as a winged adult.
Dragonflies can live a few months as adults and continue their predatory lifestyle, swooping through the air and snatching up flying prey, aided by their large eyes. The names of some of our Michigan species hint at their hunting skills: meadowhawk, Eastern pondhawk, and dragonhunter, the latter of which hunts smaller dragonflies! Dragonflies are celebrated for eating lots of mosquitoes, which are also aquatic insects.
Mosquitoes
Mosquitoes are in the insect order Diptera (from the Greek for “two-wing”), which includes all true flies. True flies have a somewhat different life cycle than mayflies and dragonflies. When mosquito eggs hatch, the larvae look very different than adults. They lack jointed legs and wings, have a wormlike abdomen and a large head and thorax. They hang just below the water’s surface with a breathing apparatus poking up out of the water like a snorkel. Larvae feed on algae and other tiny organisms, growing for about a week until they are ready to form a pupa, like the cocoon of a butterfly. The pupae float at the water’s surface and hatch after 2-3 days into an adult mosquito which flies away to mate. Female adults need a meal of blood to reproduce, which is why they bite us and other animals.
Mosquitoes are important food for fish, birds, and (that’s right!) other insects, like dragonflies. However, they can spread disease so it’s worth removing or regularly cleaning sources of standing water such as birdbaths and planters.
Michigan State University Extension invites you to take some time during the summer to watch for insects around your lake. Think about the complex life cycles and how they connect to the lives of other lake inhabitants. Protect their habitat by preserving aquatic and nearshore vegetation and preventing pollution from degrading water quality.
A version of this article originally appeared in the September 2022 issue of the Lakefront Lifestyles magazine.
