News Photo by Courtney Boyd A small group of mayflies gathered on a window near Alpena Community College. The photo was taken the first weekend of June.

ALPENA — Early last week, Alpena residents may have spotted small patches of mayflies (also known as “fish flies”) along the water or by their porch lights. While the swarm has diminished since then, more are expected to appear as summer goes on.

Mayfly season usually occurs near bodies of freshwater between June and August. During this time, the insects will hatch, fly, and mate within 48 hours before dying. Swarms have been emerging across the state as the weather warms up.

David Lowenstein is a consumer horticulture educator at Michigan State University with a background in entomology. He said the insects remain fairly close to water due to their short lifespans, and that hatch times and swarm sizes can vary greatly.

“You really have to be close to the stream or close to a lake (to see them),” he said. “A mile, one and a half miles can make or break between if you’re experiencing a lot of fish flies or it’s business as usual and you have no clue there’s even fish flies active in the area.”

Lowenstein said the trigger that causes mayflies to hatch is water temperature. Once water temperatures reach 68 degrees Fahrenheit, the bugs will start to hatch and enter the adult stages of their life cycle.

According to the National Weather Service, water temperatures in Alpena are currently hovering in the 50s. Data from the National Oceanic and Atmospheric Administration (NOAA) shows that the average water temperature in Lake Huron usually stays below 68 until August.

Despite this, temperatures in surrounding counties like Alcona, Oscoda, and Iosco are close to or above the needed threshold for mayflies to hatch. Lake Erie, Lake St. Clair, and parts of Lake Michigan are also already seeing these temperatures. Cities along Lake Erie and Lake St. Clair are also reporting mayfly swarms.

Lowenstein said that while the insects may be annoying to some, they are actually a good sign in communities surrounded by water as they indicate good water quality. He said areas that have high oxygen concentrations and less agricultural run off tend to see higher mayfly populations, while areas polluted by agricultural run off tend to see more algae blooms.

“It’s a good thing to experience fish flies,” he said. “If you don’t like fish flies and you live near a lake, turn your porch lights off for the night and keep your windows closed, but beyond that it’s just a part of Michigan summers and living near water. I think it’s a worthwhile trade off a few days of insects that some find annoying for a sign that our waterways are doing quite okay.”

This story was produced by the Michigan News Group Internship Program, a collaboration between WCMU Public Media and local newspapers in central and northern Michigan. The program’s mission is to train the next generation of journalists and combat the rise of rural news deserts.