Fireflies in decline?

Jun 21, 2018

Fireflies
Credit Photo: wypr.org

The recent rain in Athens means it’s been a good summer for lightning bugs. But UGA professor of entomology Paul Guillebeau says that like a lot of animals, their numbers are declining. He says the primary reason is loss of habitat. “If you want your lawn to look like Augusta National [Golf Club] -- and a lot of people do -- there's no place for animals. It also requires a lot of insecticides.”

Light pollution is another factor contributing to their falling population. The lightning bugs flash to signal mates and when there’s strong enough artificial illumination, like streetlights and neon signs, the insects can’t signal bright enough to attract a mate, leading to a decline in reproduction. “We’re pushing back the wild places and putting in subdivisions,” Guillebeau said. However there’s not a lot of hard data on the insect’s numbers.

Much of what we know about lightning bug populations is anecdotal or extrapolated from information on loss of habitat. Research on the insect lacks the kind of financial base for research that’s afforded to studies on controlling pests. If you want to attract more lightning bugs to your yard, Guillebeau says it’s best to keep your grass long, establish an ornamental pond or other water feature, and limit light pollution. He also clarified that while a lightning bug also goes by the name firefly, it is neither a fly nor a bug. Bugs have a piercing, sucking mouth part. Lightning bugs, which are a kind of beetle, have a chewing mouth part. “Like a pair of pliers,” he said. As beetles, they also go through a complete metamorphosis, transitioning through a larval stage and pupal stage before they become an adult.

Aside from the predaceous larvae serving as a natural pest control, he thinks the insects have an inherent aesthetic value. “Every child is fascinated by lightning bugs and that leads to appreciation of other natural things.” If you want to interact with a firefly up close, you can use a penlight in the dark to attract one and, with enough practice, get it to land on your hand.

One species of firefly uses a similar deception to its advantage. A female photuris firefly is known to blink like a photinus firefly. A male photinus will come over in hopes of mating, only to be eaten by the female.

“That’s kinda rude,” said Guillebeau. “You get yourself all cleaned up and she turns out to be a cannibal.”