Massive swarms of Mayflies show up on Detroit radar

It is now the peak season for fish flies to hatch in Lake St. Clair and Lake Erie. Fish flies, Mayflies, or shadflies emerge from bodies of water to hover around lights, cling to walls, mate and then die, all within the scope of about two days.

This year, the hatch is so abundant that the swarms can be seen on radar in Detroit every evening.

A National Weather Service tweet said: An image with the tweet shows dark blue patches representing the swarms of the fish flies over Lake St. Clair and the west edge of Lake Erie. Meterologist Cory Behnke said radar starts picking up the hatch around dusk during the last few weeks of June. As well as detecting rain and hail, the radar can sometimes see large flocks of birds emerging from bodies of water.

Fish fliesMayflies or shadflies are aquatic insects belonging to the order Ephemeroptera. It is part of a group of ancient insects which also contains dragonflies and damselflies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families.The females fly over lakes and each drops about 4,000 eggs.

The insects may be called May flies or shad flies as well as fish flies but not June bugs. Lynda Corkum, a University of Windsor biology professor explains: "This seems very peculiar, because usually, the peak emergence when you see so many on the wing is during the month of June, and that's why people want to say June bugs, but they're not June bugs. A June bug is a beetle." The insects are eaten by fish, and small mammals.

Corkum said that the flies often emerge from lakes at night: "The males will have swarms over vegetation near the water, and this will occur, depending on the species, around 8 p.m., and females will fly through the swarm ,and then a male will grab her and tumble to the ground and mate,They come out in thousands of numbers, because they only live for a couple of days, The idea is you have to find a mate in a short period of time so that's one reason why so many come out synchronously."

When young the fish flies have cloudy wings but when they are mature the wings become very shiny. The flies are attracted to ultraviolet light and often stick to storefronts. Corkum predicted the hatch would peak around June 18. As the appended video shows, the swarms can be so thick as to create a sticky mess.