By Erin Weeks
Finding a mate can be hard enough in the animal kingdom, but nocturnal creatures face an added difficulty — locating potential partners in the dark. It’s a problem many insects have solved by evolving an array of mating signals that engage all of the senses: crickets chirp, moths follow pheromone trails, fireflies glow and blink.
These signals don’t just attract other insects — they’ve also become cultural touchstones for humans. Singing crickets have been immortalized in folklore across the globe, and, at least in the West, “lightning bugs” are part of what makes hot summer nights so evocative and nostalgia-inducing.
“That’s the best thing about fireflies, they’re something people around the world have strong feelings for,” said Juang-Horng “JC” Chong, an entomologist at Clemson University in South Carolina. Those strong feelings launched Chong and another Clemson professor, Alex Chow, on a project that’s turned a simple question — are fireflies disappearing? — into a national census of the iconic insect and a citizen-science success story.
The Vanishing Firefly Project began in 2010, not long after biogeochemist Chow experienced a firefly light show for the first time. Chow, who grew up in brightly lit Hong Kong, arrived at a plantation-turned-wildlife refuge on the coast of South Carolina to study nutrient dynamics. The fireflies in the rural area put on an impressive spectacle that spring. But Chow noticed fewer fireflies after prescribed burns of the property’s forest, and he wondered if there was a correlation between the insect’s habitat use and its abundance.
No one had yet looked at the response of fireflies to prescribed burns, but researchers had long suspected that artificial light sources could affect firefly mating behavior. By outshining the insects’ light-producing organs, the idea went, artificial light could drown out communication between potential mates. Only recently, however, have field studies tested the theory. In 2012, a Swiss team confirmed that male fireflies avoided areas flooded by street-lamp light in a small village. Enough dark areas remained in the residential area that the population did not appear to be impacted, but little work has investigated what happens in habitat lacking dark refuges.
Before Alex Chow could answer this or any other questions, he needed the help of an entomologist.
“I knew nothing about fireflies, but I said, sure,” said Chong, whose expertise was instead in pest management. He signed on to the project anyway.
The first year, Chow and Chong kept things local. They decided to conduct a small-scale census on the wildlife refuge where Chow worked, and they counted the fireflies in 12 different habitat types (including a salt marsh, a logged area, a forest still recovering from Hurricane Hugo, and an open, street-lit area). Their aims were scientific, but their work has always interested a broad cross-section of the public — many of whom have wondered whether it was just their imagination that the summer evenings of their childhoods seemed to sparkle more than those of the present. For that reason, the Vanishing Firefly Project has always had a large citizen-science component. For the first census, Chow and Chong invited members of the public to join them as they counted fireflies and collected soil samples.
“Quite a few showed up,” he said. But if the team was going to develop a baseline understanding of how fireflies were faring in South Carolina and beyond, they needed a lot more help.
In 2013, the Vanishing Firefly Project rolled out a mobile app to invite anyone with a smartphone to join the census. Designed with the help of Clemson University students, the app instructs participants how to accurately count fireflies and compiles each user’s census information into a database. The results from the past two years, displayed on a map on the project website, show that most of the app’s users still come from South Carolina. But last year, census data also came in from places as far-flung as Italy and Colombia. The project’s team members hope this expanding geographic trend continues as the census grows and the app is tweaked each year.
So far, the collected data “points to fireflies as a very local animal,” Chong said. “They don’t disperse very much. That’s good if you know of a location where you can see many of the insects. The bad thing is, if you destroy that particular environment, the fireflies will be gone too.”
If the Vanishing Firefly Project succeeds at capturing long-term firefly abundance in the Southeast, a complementary program in New England could help cover the rest of the East Coast. The Museum of Science in Boston, MA has operated Firefly Watch, a similar citizen-science project, since 2008. Rather than conducting a single census, Firefly Watch asks its volunteers to report firefly numbers in their backyards over the course of each summer. Its users also report on the lawn care of their backyards. Because fireflies spend daytime hours on the ground, researchers think pesticide use and frequent mowing may adversely affect them.
Firefly enthusiasts will have three chances this summer to participate in a Vanishing Firefly Project census: June 6, July 4, and August 1. The free app is available as a download from iTunes, and it includes a tutorial to help users count firefly numbers with accuracy.
Many more years of data are needed before scientists can definitively answer whether fireflies are vanishing. But as long as citizen science projects abound, these beloved insects won’t disappear without a trace.