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Rain, Cooler Air Help Boost Firefly Population in Portions of US

By By Mark Leberfinger, Staff Writer
August 21, 2014, 5:22:11 AM EDT

Above-average rainfall and cooler air have led to a boom in the firefly population in parts of the United States.

“States in the South seem to actually benefit from the cooler temperatures and more abundant rainfall," Ben Pfeiffer, founder of the website, said. "We have strong reports from places like West Virginia, Georgia, Tennessee and other areas of abundant fireflies this year. One person emailed and told us she had so many fireflies on West Virginia roads they covered her windshield and car while she was driving.”

From June 1 through Aug. 13, it has been cooler and rather wet in parts of the South, according to Senior Meteorologist Dan Pydynowski.

Atlanta has received 13.72 inches, or 127 percent of normal, and Raleigh, North Carolina, has received 174 percent of normal at 17.39 inches, Pydynowski said. The two cities, respectively, are 1.2 degrees and 0.8 degrees below normal.


Fireflies used to be harvested for luciferase, a chemical they use for light production and has many uses in the biological and medical field as a reporter chemical, Don Salvatore, coordinator of the Firefly Watch program at the Boston's Museum of Science, said. Firefly lanterns are also being studied for how to produce a more efficient lighting system in LED production.

Firefly Watch has been in existence since 2008, Salvatore said. More than 5,000 people in 40 U.S. states and six Canadian provinces participate in the project.

Fireflies are important biological indicators of environmental health, Salvatore said.

“We have found in our project that people care about fireflies enough to change some of their habits to help preserve them,” he said. “These changes may include reduced or discontinuance of use of pesticides in their backyard, changes in mowing habits and turning off night lights that may affect firefly communication."

“They are a good indicator of environmental health because when their numbers decline, people notice," Salvatore said. "If all of the crane flies in an area disappear, no one other than a few entomologists would notice. However, if fireflies disappear, everyone notices and become concerned.”

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While some areas of the U.S. are seeing a boom in fireflies, others have declining populations.

“In areas that are getting hotter and having more extended period of drought, fireflies are struggling," Pfeiffer said.

Light pollution and drought also play roles in the number of fireflies, Pfeiffer added.

“Some species of fireflies are extremely sensitive to light pollution. The main species, Photinus pyralis (or common eastern firefly), is a bit more hardy and tends to tolerate some light,” Pfieffer said. “Light pollution can impact firefly mates seeing each other in the forest. If a female flashes and the flash is obscured by light pollution or whatever, there is less chance a male might see it.

Fireflies continue to capture people’s imagination, Salvatore and Pfeiffer said.

“Children love them because at night, when it is dark and scary out, firefly light seems to speak directly to a child and reassure him or her because of the gentle nature of a firefly,” Salvatore said. “Adults also enjoy fireflies, although many feel that watching fireflies is a child’s activity. So many adults want to share their love of fireflies with children.”

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