Amid reports of firefly declines, you can help these iconic summer insects in your own backyard
A firefly flashes as the full moon rises in an Iowa backyard. Homeowners can help these beloved insects by providing habitat, avoiding pesticides, and dimming lights.
FOR MANY OF US, seeing the flash of fireflies on a warm summer night counts among our fondest childhood memories. Sadly, kids today may have far fewer opportunities to enjoy such magical sights.
Anecdotal reports from across the country and around the world suggest that fireflies are declining or even disappearing in many places. “We have no definitive proof,” says biologist Ben Pfeiffer, founder of Firefly.org, “but there is a broad consensus that fireflies are in trouble, especially locally adapted species.”
Because scientists lack historic data on firefly numbers, proof may be hard to come by. In some cases, “we still debate what constitutes a species,” says Eric Lee-Mäder, pollinator program co-director for the Xerces Society for Invertebrate Conservation. “Are two morphologically identical fireflies with different flash patterns two species—or one species with individuals speaking different languages? If we can’t answer that, how can we know how the insects are doing?”
To find out, his organization this spring launched a nationwide conservation status review of North America’s nearly 200 firefly species. Lee-Mäder says he won’t be surprised to discover bad news: “When you combine the number of reports of population declines with the number of threats, it’s a good indication there is a problem.”
Threats include pesticides and habitat loss, which also harm other imperiled insects such as bees. Hazards unique to fireflies are light pollution and a long history of collection by the biomedical industry for the light-producing enzymes fireflies make.
“The good news,” says Pfeiffer, “is that fireflies are relatively robust, and homeowners, especially gardeners, can encourage the insects to colonize their yards.” Here’s how:
Provide larval habitat. Firefly eggs hatch and larvae develop in rotten logs and leaf litter. Let fallen leaves, branches and other organic matter pile up in parts of your yard.
Give adults food and shelter. Adult fireflies live and feed in long grasses—and females climb tall stems to flash to males overhead—so do not overmow. In some cases, these carnivorous insects eat flower nectar as adults; plants in the Asteraceae family may be especially attractive.
Supply water. Fireflies thrive around ponds, springs, and puddles.
Avoid pesticides. Broad-spectrum lawn chemicals are especially deadly. Let fireflies control your grubs, slugs, and snails naturally.
Dim the lights. Scientists suspect fireflies are harmed by light pollution, which disrupts the flashes the insects use to communicate. Dimmer lights may also enhance your experience of fireflies, forging brand new memories of summer’s magical nights.
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Laura Tangley is senior editor.
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