Post by Jen Berlinghof
At a recent Firefly Campfire at Ryerson Conservation Area, kids and adults alike were flitting around, as fast as the fireflies they were trying to catch. For many of the children, this was their first time experiencing the age-old summer tradition of capturing living light. While the woods that night sparkled like the fourth of July, many of the adults lamented that their yards didn’t have many fireflies—certainly not like the numbers they remembered chasing as children. Turns out they may be on to something.
Widespread anecdotal evidence of these dwindling evening displays have prompted scientists to take a look at possible reasons. One big culprit to the demise of these bioluminescent beetles seems to be the one thing that makes them so special: light.
Fireflies are one of the few groups of insects that use sight instead of smell or sound to find mates. Each firefly species has a unique series of flashes that help them defend territory, warn predators, and create courtship conversations. Males flash a code in flight. Females hang out on nearby vegetation, watching the show and flashing back the same sequence if a prospective suitor catches her compound eye.
Increased light pollution from human technology and development (think cars, homes, streetlights, stores) may be causing a breakdown in the visual communication between fireflies. A male’s signals can get lost in the shuffle or are misread by females. The result is less mating, therefore, fewer firefly eggs laid.
Another factor extinguishing these summer light shows is that fireflies are losing their “stage.” Fireflies breed and live in forests, marshes, unruly fields, and dense gardens. The larvae (“glow worms”) don’t stray too far from where they hatch. As habitats disappear, so too do all the critters that call them home. This is one reason why the parents and children at the Firefly Campfire had no trouble finding fireflies to catch and release, over and over again, late into the evening in the Lake County Forest Preserves. The natural habitat is intact in these areas, providing plenty of food, shelter, and darkness for fireflies to “talk.”
Since the preserves close at sunset, we offer special evening opportunities to enjoy nature at night. We will remain open for a Summer Night Hike and a Community Campfire, where you can catch a glimpse of the firefly glimmer.
Want to help firefly populations and set the scene for a personal light show in your yard? Consider landscaping with native plants, which lessen or eliminate the need for chemicals on your lawn and garden because they are adapted to local conditions. Pesticides can shrink the food supply of fireflies, who as larvae feed on slugs, grubs, and worms. Chemicals can also discourage adult female fireflies from the area, who wait in grasses and low shrubs for the males’ signals. Additionally, consider turning off or reducing exterior lights at night to attract and enjoy nature’s own sparkling illumination.
I also never see mayflies anymore. In Grayslake we used to see great clouds of them lift off the lake and settle on the sides of trees~no more. I worry that mosquito abatement programs may be doing them in.
Thanks for reading. Mayfly populations are directly affected by changes in oxygen levels in the water. As water chemistry changes, such as increased phosphorus from runoff, this cause changes in our aquatic systems and can lead to reduced oxygen levels. Changes in emergence densities can warn of harmful changes in the water.
Typically mosquito abatement programs use larvicide that targets mosquitos during that phase of life. However, there are some chemicals that can harm other aquatic organisms if applied improperly.
Thank you for posting this. Light pollution seems to be something which is often overlooked. The Boston Museum of Science has a citizen science firefly watch program if anyone is interested. https://legacy.mos.org/fireflywatch/about_firefly_watch
Thanks for sharing!