‘From its enzymes to its role in the food chain, the little firefly is a big part of the cycle of life’

Sara Lewis, professor emerita of biology at Tufts University, is co-chair of the IUCN Firefly Specialist Group. Speaking to Srijana Mitra Das at Times Evoke, she discusses firefly species worldwide:
What is the core of your research?
I work with 45 experts from across the world for the International Union for the Conservation of Nature (IUCN). Our goal is to support studies of firefly biodiversity globally, to understand how many species there are, what conditions they need to survive, which are the most imperilled groups and how we can work with governments, communities and agencies to help protect these jewels of the night.

ALL THAT GLITTERS ISN’T JUST GOLD: Fireflies are loved world over for their bioluminescence — their presence indicates healthy and stable ecosystems. Photo courtesy: iStock
How many firefly species exist?
There are about 2,200 described species of fireflies but it’s likely there are plenty more which haven’t been chronicled yet. The traditional way of distinguishing between them is based on morphology — studies over hundreds of years now have researched tiny details of the forms of fireflies. Sometimes, there are large differences in how they look or minute internal distinctions. There are also differences in behaviour — fieldwork helps distinguish between species which may look practically identical. We’ve recently also used DNA sequences to understand diverse species.

SHINE, KINDLY LIGHT: The ‘glowing’ firefly enzyme helps in cancer drugs. Photo courtesy: iStock
Do fireflies play an ecological role?
Fireflies are appreciated for their beauty around the world. But they also make very important practical contributions — the gene for the enzyme luciferase, which allows fireflies to make their light, is a crucial scientific tool, spanning agricultural research to biomedicine.
This enzyme has helped us understand how different genes are regulated — it’s also enabled us to develop drugs against cancer and generate drought-resistant crops. Fireflies themselves are beetles who go through metamorphosis — as juveniles, they are predatory beings and eat snails, slugs and earthworms. So, they control agricultural pests. While not every animal can eat fireflies directly — they are toxic to many birds — frogs, spiders and other insects prey on them and are then eaten by birds higher up in the food chain. So, the little firefly is actually a very important part of the cycle of life. Fireflies also change their nature startlingly — these ethereal sparks of light who, as adults, don’t eat anything, come from a juvenile stage, living in leaf litter and underground, when they were really voracious, tough hunters. These fascinating beings then switch into a very different lifestyle.
Do fireflies confront existential threats?
Fireflies evolved their bioluminescence in order to signal in complete darkness — but as humans have illuminated the nocturnal world more and more with artificial light, detecting this signal has become much harder for them. Recently, we’ve demonstrated this negative impact and how this is especially true for species whose signalling time is only when it is completely dark. Some fireflies can signal at dusk but others are fully nocturnal — for them, artificial light of any colour really impacts mating success. Studies over the last ten years have observed different species’ reactions to varied colours and their intensities — it’s confirmed that artificial light reduces the courtship signalling of males and lowers female responses.


JUST 2,198 MORE: Scientists have found thousands of firefly species.Photo courtesy: iStock
For North American fireflies, a courtship dialogue takes place where the male flies around, advertising his presence, and the female responds. Artificial light diminishes the male advertisement rate and reduces the female’s rate of response to male signals — they can’t find each other. This is also true of glow-worm fireflies in Europe — artificial light at night negatively impacts the ability of males to find glowing females. For different firefly groups, using varied bioluminescence signalling systems, artificial light quashes courtships and ends any romance. Among other major threats fireflies face globally is the loss of habitat, from meadows to marshes, which they need to survive. With urbanisation and growing city sprawl, firefly habitat has been cut into. In the US, fireflies were once widespread but as their territory decreased, they are dwindling away now. Consider mangrove fireflies — many live only there and eat just one kind of mangrove snail. In Southeast Asia, these are declining now as mangrove forests are being replaced by oil palm plantations and shrimp farms. Scientists are researching the impacts of climate change as well. Firefly species need a certain amount of moisture through all their life stages — precipitation extremes, from heavy rain to drought, could have a negative effect.

How can people help conserve fireflies?
We don’t think of fireflies as often as we consider big charismatic animals like tigers — yet, as I term them, these are mini-charismatic fauna. It is very important to appreciate them and the conditions in which they thrive. Urban dwellers worldwide will remember how around a generation ago, you could see fireflies fairly often — now, it’s rare to see a firefly in a city park. We must protect the areas where they are still found — people can write to town officials and city governments to safeguard firefly zones now, so they can survive into the future. Also, advocate for reducing local light pollution — and where possible, don’t leave extra lights on.