The Mayfly: is James Dean of Insects is Good News for the L.A. River

The Los Angeles River and its environs is home to a wealth of flora and fauna. This series of posts on Confluence attempts to unveil the hidden wildlife that thrives along the river banks.

Insect swarms can sometimes conjure images of Biblical plagues, but if it's a huge gathering of mayflies, we shouldn't fear, we should celebrate, says Lila Higgins, manager of citizen science at the L.A. County Natural History Museum (NHM) and program coordinator for Play the LA River. These aquatic insects are actually indicators of health, says Higgins.

Unlike a gathering of flies over rotting food (or over anything really), the presence of a mayfly horde indicates excellent water quality. The mayflies spend 99 percent of their lives at the river bottom, feeding on algae, decomposing matter, and they need clean water to survive.

Biologists run complex tests on water quality all the time, but whenever they see mayflies, they breathe a sigh of relief. Kent Johnson oversees environmental quality in the greater Minneapolis-St. Paul area and calls them a biologist's environmental cheat sheet.

Throw your hands up in the air and celebrate the thriving mayfly population that keeps our L.A. River nice and healthy. Photo by Jeffcapeshop, Flickr Creative Commons License.

But more than a simple way to tell a water source's cleanliness, the mayfly in itself is an interesting subject of study. Although the word fly appears in their names, these insects aren't really flies. Mayflies are their own group of insects, says Higgins, Just like there's a group of butterflies, moths, honeybees, ants, and wasps.

There are more than 3,000 described species that we all call mayflies. They're a whole order of insects unto themselves, said Higgins, There are just so many of them, people don't know what they're about. Encyclopedia Britannica says many species of mayflies are still waiting to be discovered or described. This despite the fact that these insects have been in existence for a very long time-about 290 million years ago during the late Carboniferous or early Permian periods.

A mayfly lives a fleeting life as an adult. Once they mature, their lives can last as little as a few hours or as long as a couple of days. This is why their order name, Ephemeroptera, comes from the Greek word ephemeros meaning, lasting but a day. Their common name comes from their predisposition to come out in swarms during the summer months, particularly May. Other common names include June bug, Canadian soldier, or fishfly.

In its brief adult life, the mayfly leaves out nonessential activities, like eating, to focus on its true purpose -reproduction. Photo by Mark Robinson. Flickr Creative Commons License.

Old-school mayfly: Fossil adult Mickoleitia longimanus(Coxoplectoptera: Mickoleitiidae) from the Lower Cretaceous Crato Formationof Brazil, c. 108 mya. By Dr. G nter Bechly (Own work), via Wikimedia Commons.

But despite the brevity of their lives, they go out in a blaze of glory. When these insects mature, they insects develop wings, fly out of the water in swarms, and mate. They appear in so large a drove that they are known to cover houses, cars, buildings, and roads. Swarms can be so spectacular, they show up on radar.

According to Leslie Mertz of Know Your Insects, mayflies have a one-track mind as adults. As full adults, these insects don't have functional mouths for eating, their whole purpose is reproduction.

Once the ritual is done, the female descends to the surface of the water, laying her eggs-which can be as many as 8,000 eggs -and lies spent and dying. The male wanders toward land and also dies. Their eggs fall to the bottom of the water, where they hatch, repeating the cycle again.

A mayfly isn't just fascinating because of its James Dean lifestyle, these insects are an important food source for many animals that live by the water. As they fly, birds, bats, dragonflies all snack on them. While they rest, these insects are preyed upon by spiders, beetles, even flying squirrels. Right after mating, as a female drifts to the water's surface, fishes are also closing in on them. They're such a part of the food cycle that fishermen often have artificial lures designed to look like mayflies. Higgins has seen mayflies be devoured as they fly by birds circling above the river's water.

So the next time, it gets a little dark by the river, and you see a swirl of something above the water, check your goose bumps, and bring out your binoculars, you're witnessing a ritual that has repeated over millennia.

Mayfly fishing flies, from Charles and Richard Bowlkers Art of Angling, 1854. Wikimedia Commons.

Top image by Rob Widdicombe.

LINK:	https://www.kcet.org/confluence/the-mayfly-this-james-dean-of-insects-...
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