Huge summer for fireflies means backyard fireworks for us, frenzied flirting for them

Meg Jones
Milwaukee Journal Sentinel

 

Fireflies are back and they're blinking like crazy this summer.

Many backyards, rural roads and fields throughout Wisconsin have turned into miniature versions of the flashing Vegas strip thanks to a soaring firefly population.

"It's a huge year for fireflies in many areas," said University of Wisconsin-Madison entomologist Dan Young, director of UW's insect research collection. "I've never seen this many in my backyard."

Fireflies like wet, moist conditions, particularly when they're in the larval stage. They prefer dining on slugs as well as millipedes, land snails and other soft-bodied invertebrates that thrive in dampness. So if it's a good year for slugs, it's a good year for fireflies.

A composite of multiple images over the span of about five minutes shows the mass of fireflies lighting up the night at the Schlitz Audubon Nature Center in Bayside.

Frequent rains this spring — Milwaukee got 3 inches more than normal for the April-May-June stretch — have been the human equivalent of sunny and 72 degrees for lightning bugs.

At Schlitz Audubon Center in Bayside, a group of volunteers participated July 6 in a weekly survey that's part of Museum of Science, Boston Firefly Watch.

Researchers hope to learn, among other things, whether light pollution in growing urban areas is affecting fireflies. In addition to recording cloud cover and moonlight, wind speed, precipitation, ambient light and habitat, volunteers count the number of fireflies they see: zero, 2-5, 6-20 and more than 20, as well as color and frequency of flashes.

"When we were out last week we saw hundreds. It was just amazing. We thought it was a late Fourth of July firefly celebration," said Moya Mowbray, who is leading the Schlitz Audubon firefly volunteers.

"You're supposed to count how many you see in 10 seconds and I couldn't count that fast," added Schlitz Audubon volunteer Kathy Brehmer. "I just checked the box that said more than 20."

Want to date?

Fireflies aren't just showing off; all that flashing creates the equivalent of a firefly singles bar. While females typically perch on grass or fly low to the ground, males zoom around above the females flashing a date-seeking Morse code. Sparks fly when a female detects an attractive flasher and signals back.

Each firefly species, and there are roughly two dozen in the Great Lakes region, flashes a different signal to attract mates. Some flash only once, some flash multiple times, some flash while flying a pattern. A species nicknamed big dipper (actual name: Photinus pyralis) fly downward and then zip up, painting a "J" or dipper with their glowing tail, said Young. 

Fireflies, which are beetles, also differentiate themselves with colors; some glow yellow while others are blue or sport a greenish hue, said UW Extension entomologist P.J. Liesch.

A couple of fireflies hang together on a blade of grass.

Their light-making prowess — they're not called "lightning bugs" for nothing — is incredibly efficient, transforming almost 100% of their energy into light through a complex reaction of proteins.

"When we think of most lights humans have produced, the energy is coming out as heat," explained Young. "But because these are proteins, proteins don't like heat at all. So for them to light up, they have to be able to produce cold light."

Then there are the femme fatales of the firefly world. Female lightning bugs of the genus Photuris mimic the flashing pattern of another species to lure males, who think they're hooking up with a female of their kind. When the males draw close, they're eaten.

Fireflies lay their fertilized eggs on or just below the surface of the ground, with the eggs hatching about a month later. Larvae feed for the rest of the summer and then spend the winter still in the larval stage burrowed underground or under tree bark.

In late spring, larvae pupate and transform into adults. And right about now, they're looking for ... ahem ... company. Depending on weather, it's likely the firefly peak is happening right now in Wisconsin, said Liesch.

"They're not long-lived. They're out there trying to advertise and mate. They may live for only a couple of weeks," Liesch said.

Anyone is welcome to participate in the firefly surveys at Schlitz Audubon Nature Center, 1111 E. Brown Deer Road, Bayside, which start around 8:30 p.m. and will be held July 18, July 26 and Thursdays in August. For more information, contact: mmowbray@schlitzaudubon.org