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Sunday, March 8, 2020

Save the fireflies

Fireflies threatened by habitat loss, pesticides, artificial light
By Science News Staff / Source

Allyouneediswall night magic tree calm GIFSince their evolutionary origin some 297 million years ago, beetles have been highly successful; they represent 38% of known insect species. 

Fireflies rank among the most charismatic beetles, with distinctive bioluminescent courtship displays that make them a potential flagship group for insect conservation.

With more than 2,000 species worldwide, fireflies exhibit surprisingly diverse life history traits, including nonluminous adults with daytime activity periods, glowworm fireflies with flightless females, and lightning bugs that exchange species-specific flash signals.

Fireflies also inhabit ecologically diverse habitats, including wetlands, grasslands, forests, agricultural fields, and urban parks.

Their predaceous larvae, which can be aquatic, semiaquatic, or terrestrial, spend months to years feeding on snails, earthworms, and other soft-bodied prey. In contrast, firefly adults are typically short lived and do not feed.

Fireflies are economically important in many countries, because they represent a growing ecotourist attraction. However, as is true for many invertebrates, fireflies have been largely neglected in global conservation efforts.

To better understand what threats are faced by fireflies, Tufts University’s Professor Sara Lewis and colleagues surveyed firefly experts around the world to size up the most prominent threats to survival for their local species.

“Lots of wildlife species are declining because their habitat is shrinking, so it wasn’t a huge surprise that habitat loss was considered the biggest threat,” Professor Lewis said.

“Some fireflies get hit especially hard when their habitat disappears because they need special conditions to complete their life cycle.”

“For instance, one Malaysian firefly (Pteroptyx tener), famous for its synchronized flash displays, is a mangrove specialist.”

One surprising result that emerged from the survey was that, globally, light pollution was regarded as the second most serious threat to fireflies.

“In addition to disrupting natural biorhythms — including our own — light pollution really messes up firefly mating rituals,” said Avalon Owens, a Ph.D. candidate at Tufts University.

Many fireflies rely on bioluminescence to find and attract their mates, and previous work has shown that too much artificial light can interfere with these courtship exchanges. Switching to energy efficient, overly bright LEDs is not helping.

Firefly experts viewed the widespread agricultural use of pesticides as another key threat to firefly survival.

Most insecticide exposure occurs during larval stages, because juvenile fireflies spend up to two years living below ground or under water. Insecticides such as organophosphates and neonicotinoids are designed to kill pests, yet they also have off-target effects on beneficial insects.

While more research is needed, the evidence shows that many commonly used insecticides are harmful to fireflies.

A few studies have quantified firefly population declines, such as those seen in the tourist-attracting synchronous fireflies of Malaysia, and the glowworm Lampyris noctiluca in England. And numerous anecdotal reports suggest that many other firefly species across a wide range of habitats have also suffered recent declines.

The researchers also highlight risk factors that allow them to predict which species will be most vulnerable when faced with threats like habitat loss or light pollution.

For instance, females of the Appalachian blue ghost firefly (Phausis reticulata) are flightless.
“So when their habitat disappears, they can’t just pick up and move somewhere else,” said Tufts University’s Professor J. Michael Reed.

“Here in the U.S., we’re fortunate to have some robust species like the Big Dipper fireflies (Photinus pyralis),” Professor Lewis said.

“Those guys can survive pretty much anywhere- and they’re beautiful, too.”

By illuminating these threats and evaluating the conservation status of firefly species around the world, scientists aim to preserve the magical lights of fireflies for future generations to enjoy.

“Our goal is to make this knowledge available for land managers, policy makers, and firefly fans everywhere,” said Dr. Sonny Wong, of the Malaysian Nature Society.

“We want to keep fireflies lighting up our nights for a long, long time.”

The report was published in the journal BioScience.
Sara M. Lewis et al. A Global Perspective on Firefly Extinction Threats. BioScience, published online February 3, 2020; doi: 10.1093/biosci/biz157