The Flight of the Mayflies

The annual emergence of mayflies, wherever it occurs, brings predictable responses.

September 14, 2019 | | Notes from the Wild

Mayflies rise like tiny white angels from the surface of the Credit River in August. At first only a few, fluttering. Then a flurry of gossamer-winged insects trailing filamentous tails that quickly builds into a blizzard. A blizzard driven not by wind, but by the imperative to reproduce.

Mayflies in flashlight beam between bridge and river. Photo by Don Scallen.

Mayflies in flashlight beam between bridge and river. Photo by Don Scallen.

They live only briefly as adults. Their genus name, Ephemeroptera (essentially meaning winged ephemeral insects) is apt. One year in the stream as larvae, perhaps an hour as winged adults before they die.

Thousands get distracted from mating by streetlights during this precious hour. Great swarms orbit these lights and then drop dead to the asphalt below where they collect in drifts.

Mayflies in spider web. Photo by Don Scallen.

Mayflies in spider web. Photo by Don Scallen.

And some females seem to mistake the smooth asphalt for water, landing and laying their strings of orange eggs on the tarmac instead of the surface of the river.

The lure of lights is puzzling but is probably related to the challenge that hatchling sea turtles face on ocean beaches adjacent to urban areas. In natural settings, light reflecting off the ocean surface guides turtles to the surf. But hotel and condominium lights can draw the turtles inland to their doom.

A river flowing through natural darkness reflects moonlight and even starlight, guiding the mayflies upstream. Even in overcast conditions the rivers likely offer more reflected light than the surrounding landscape.

Mayflies on Credit River bridge. Photo by Don Scallen.

Mayflies on Credit River bridge. Photo by Don Scallen.

The annual emergence of mayflies, wherever it occurs, brings predictable responses. As I stood on a bridge in Glen Williams this year, smitten by the spectacle, a woman hurried by muttering “ugh!” and “gross!” Sad, and indicative of the ignorance that taints our relationship with bugs.

Mayflies have great ecological value, but they are also beautiful, and their brief flicker of existence is a poignant reminder that life, theirs and ours, is transitory.


Read more about mayflies in Don Scallen’s “River World” article in the fall issue of In The Hills.

Mayfly Videos

Mayflies in flight.

Close up of mayflies in flight.

Mayflies in flashlight beam between bridge and river.

About the Author More by Don Scallen

Don Scallen enjoys sharing his love of nature through his writing and presentations. Check out his blog "Notes from the Wild".

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