Published on February 17, 2020

Fireflies Around the World

by Sara Lewis

Timelapse image of fireflies in a field in Idaho © Theron Jensen
© Theron Jensen

Over the past few decades, we've learned so much about fireflies! Thanks to diligent efforts by many scientists, we know quite a lot about different fireflies from all around the world. Yet for most species, we're still missing a critical piece of information—what are their long-term population trends?

By collecting data on how firefly numbers change over time at a single location, citizen scientists can help identify species that are in trouble. Then we can take action, using our knowledge about firefly ecology to protect these treasured insects.

Thailand is home to many flashing fireflies, including several species of synchronously flashing Pteropytx. Hundreds of these males gather nightly in particular display trees, all flashing together in unison to attract females. Some Pteroptyx malaccae live surprisingly close to Bangkok in mangrove forest on the unspoiled island of Bang Kachao. There, Dr. Anchana Thancharoen has established a Firefly Conservation & Education Center that trains volunteers ranging in age from 8 to 80.

I visited there last summer to give a presentation about firefly conservation, and had a chance to see one of the firefly survey teams in action. Walking along a raised bike path that runs through the forest, survey team members count display trees and estimate how many male fireflies are flashing in each one. After the government installed LED lights to illuminate the bike path, these monthly surveys are helping firefly researchers understand how these bright light impact the fireflies.

Perhaps the longest-running firefly survey has been going on in England, focused on a firefly known as the common European glow-worm (Lampyris noctiluca). These females are wingless so they cannot fly. Instead, they climb onto perches where they will glow for hours to attract their flying but unlit males.

Walking slowly along a route, participants in the UK Glowworm Survey tally up the number of glowing females that they spot. Such repeated surveys taken at glowworm sites around the country provide estimates of changing population sizes. In some locations these observations now span nearly 20 years, revealing steady declines in some populations, most likely due to loss of appropriate habitat and light pollution.

Like Mass Audubon's Firefly Watch, these citizen science projects and other monitoring studies are capturing important long-term data that will help us distinguish between those firefly species that are doing fine and those in trouble. With this information in hand, we can then work together and find ways to reduce their threats and protect the most threatened species.

Dr. Sara Lewis is a Professor of Biology at Tufts University, with expertise in the courtship and mating behavior of North American fireflies.