The yellow-green streaks of fireflies that bring a magical air to summer nights, inspire camp songs and often end up in jars in children’s bedrooms may be flickering out in the backyards of the US as suburban sprawl encroaches on their habitats.
Scientists concerned by reports from the public that they are seeing fewer of the luminous insects each summer have turned to a network of backyard volunteers spanning much of the nation to track their range and numbers.
The Firefly Watch volunteers’ work is winding down now that the insects’ annual light show is over in all but southern states.
Helen Mester of South Bend, Indiana, is one of about 700 volunteers who entered observations this summer of firefly numbers, the color of their lights and flash patterns into the online database maintained by Firefly Watch, which is sponsored by the Boston Museum of Science.
The 54-year-old retiree has counted fireflies for three years for the program from her living room window or her deck.
About 200 firefly species found east of the Rocky Mountains produce, through a complex chemical reaction, lights ranging from yellow-green and yellow-amber to a pale blue. Light-producing fireflies aren’t found west of the Rockies.
Since the online Firefly Watch debuted in May 2008, about 5,100 people from 42 states have entered firefly data they collected in their yards, local parks and meadows, said Paul Fontaine, the Boston museum’s vice president of education.
Fontaine said the museum is committed to operating the program and database for at least 10 years to provide a year-to-year snapshot of firefly distribution.
The program, which also has volunteers in Canada, Costa Rica, Ghana and India, asks participants to watch fireflies for at least 10 minutes each week. Scientists at Massachusetts’ Fitchburg State University and Tufts University are helping with the project.
The data accumulating in the Firefly Watch database may help determine if fireflies are really declining, and if so where it’s happening and what could be causing it, said Christopher Cratsley, a Fitchburg biology professor who studies fireflies.
Cratsley said replacing meadows and fields with strip malls and parking lots clearly cuts firefly numbers. There is also evidence that the glare of streetlights that come with urban sprawl may interfere with the courtship of some firefly species by washing out their flashes.
He said pesticides, fertilizers and other chemicals could also kill the creatures that firefly larvae feed on, but the extent of that impact is unclear.
Georgia Southern University firefly researcher Jonathan Copeland believes the survey’s main contribution will be helping to pin down firefly species’ distribution. He said the question of whether firefly numbers were shrinking could only be answered by intensive study of specific locations over decades.
“The main value is if they are occurring and where they’re occurring,” said Copeland, a professor of biology.
San Antonio resident Denise Gregoire, who isn’t a Firefly Watch participant, lives in the same home where as a child she chased fireflies with friends. Nearly four decades after her parents moved to the home, the summer nights around it are devoid of fireflies.
Gregoire blames development — apartments, houses, a hospital complex — that replaced the fields that once surrounded her home, and the bright security lights that came with it.
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