- For years, naturalists and conservationists have noted, anecdotally, that fireflies seem to be in decline, but little was known about their conservation status, until now.
- An assessment of the extinction risk for firefly species in Canada and the U.S. reveals that 11% are threatened with extinction, 2% are near threatened, 33% are categorized as least concern, and more than half are data deficient, according to IUCN Red List criteria.
- Fireflies need abundant food sources (like snails and slugs), plenty of leaf litter and underground burrows, clean water, diverse native vegetation, and dark nights. Protecting and restoring high-quality habitat is critical for the conservation of fireflies and other insects, which are seeing global declines.
- The article includes a list of things individuals can do to help fireflies including mowing less or replacing lawns with diverse natives, leaving leaf litter, and eliminating pesticides and outside lights.
Iconic, romanticized, and celebrated, fireflies illuminate the evenings and twilight memories of people around the globe. For years, naturalists and conservationists have noted, anecdotally, that fireflies seem to be in decline, but little was known about their conservation status, until now.
Researchers from the Xerces Society, the ABQ BioPark, and the IUCN Firefly Specialist Group have just completed the first assessment of the extinction risk for firefly species in North America, covering 77% of known species in the U.S. and Canada.
Of the 128 species evaluated, 14 species (11%) are threatened with extinction, 2% are near threatened and 33% were categorized as being of least concern, according to the IUCN Red List of Threatened Species criteria. More than half of the species are listed as data deficient, meaning there not enough information to assess whether they’re at risk.
“These assessments — the first for fireflies — lay the groundwork for firefly conservation in the U.S. and Canada,” Candace Fallon, a senior conservation biologist at the Xerces Society and IUCN Red List co-assessor, said in a statement. “With this information, we can now be more strategic about setting conservation priorities and addressing data gaps, working to protect the full diversity of fireflies and their habitats, from the common and widespread big dipper firefly to the threatened and little-known southwest spring firefly.”
The most threatened species of firefly, the Bethany beach firefly (Photuris bethaniensis) is found only along a 32-kilometer (20–mile) stretch of coast in the U.S. state of Delaware, where it lives in freshwater-fed depressions among the sand dunes. Although the species is listed as endangered at the state level, plans for a nearby housing development threaten the largest known population of the firefly, and an assessment to list the species under the federal Endangered Species Act is pending.
Fireflies are not flies, but beetles in the family Lampyridae, and they are found on every continent except Antarctica. The firefly family includes the popular blinking types, glowworms and daytime dark fireflies, which communicate without blinking. In the U.S. and Canada, 114 species are flashing fireflies, 24 are glowworms, and 30 are daytime dark flies.
The green, yellow or red lights emitted by fireflies are produced through an internal chemical reaction between oxygen, a luciferin molecule, and an enzyme called luciferase. The glowing property of luciferase has been used in research to detect blood clots, understand Parkinson’s disease, visualize HIV, and develop cancer treatments.
Scientists believe fireflies and their larvae glow to warn predators that they are toxic. Fireflies contain the toxic compounds called lucibufagins, which they use as a defense against predation by birds and amphibians. (Though it doesn’t stop spiders from eating them.)
Some fireflies have adopted this glow for use in courtship. In the mountains of the U.S. states of Tennessee and North Carolina, as well as in Japan, tourists flock to witness dazzling displays of fireflies synchronizing their mating flashes.
Fireflies are threatened by habitat destruction and degradation, pesticides, light pollution, poor water quality, invasive species, overcollection, and climate change. Adults typically live less than a month, but their larvae live up to two years, so it’s primarily threats to larvae that threaten the beetles.
Most firefly larvae require wet and damp habitats such as streams, wetlands and damp fields to survive. These wet places are jeopardized by commercial and residential development, road building, water pumping, and water pollution from construction and agriculture.
The increasing number and brightness of artificial lights in North America now mean that more than 80% of people cannot see the Milky Way from where they live. This rise of artificial sky glow affects many species of animals, including fireflies, of which three-quarters are nocturnal and rely on their flashing to attract mates and deter predators. Some species require complete darkness for mating to occur and are particularly sensitive to light pollution.
Pesticides used in agriculture and for mosquito control are also harming populations, as is climate change, which has increased the intensity and frequency of droughts and wildfires in firefly habitat. Invasive species such as the red imported fire ant have been known to kill firefly larvae and contribute to firefly declines in the southeastern U.S.
“The good news is that everyone can play a role in bolstering firefly populations,” said Anna Walker, New Mexico BioPark Society species survival officer at the ABQ BioPark and Red List co-assessor. “We can turn off lights at night to reduce our individual contributions to light pollution, we can participate in community science projects like Firefly Watch that gather data on firefly distribution and abundance, and we can support organizations that protect and restore the habitats that fireflies need.”
Fireflies need abundant food sources, plenty of leaf litter and underground burrows, clean water, diverse native vegetation, and dark nights. Protecting and restoring high-quality habitat is critical for the conservation of fireflies and other insects, which are seeing global declines.
On average, the decline in global insect abundance is thought to be around 1-2% per year or 10-20% per decade.
“By identifying these threatened fireflies and understanding what they need to thrive,” said Sara Lewis, co-chair of the IUCN Firefly Specialist Group and Red List reviewer, “we’re working to ensure these wondrous insects will be lighting up night skies for future generations to enjoy.”
Here are some things you can do to protect fireflies and other insects:
- Leave areas of leaf litter on your land or lawn.
- Mow less, or better yet, replace your lawns with native plants.
- Use fences to keep cattle out of fragile wetlands.
- Reduce ground-disturbing activities or do them on a rotational basis.
- Reduce or eliminate the use of chemical fertilizers and pesticides (especially broad-spectrum pesticides like neonicotinoids).
- Allow slugs and snails to live. Firefly larvae love to eat them!
- Eliminate invasive species.
- Reduce unnecessary outdoor lighting and close your blinds at night.
- Participate in community science projects like Firefly Watch.
- Learn more about threats to fireflies and what you can do to help.
Banner image of fireflies by Fred Huang via Flickr (CC BY-NC 2.0).
Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough_
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