Fireflies, the magical glow-in-the-dark insects have always been a source of delight in spring and early summer nights. According to some estimates, they have been around since the age of the dinosaurs. But will they survive this age, overpowered by habitat loss, climate change, and light pollution? TreeTake takes a look…
“My fancies are fireflies. Specks of living light twinkling in the dark.” — Rabindranath Tagore
Do you remember a dark summer night in your childhood, when you were mesmerised by the ethereal enchantment of a glow in the bushes in your garden? You were told they were fireflies or glow worms or lightning bugs (jugnu in Hindi), which were a living example of the adage that 'nothing can dim the light that shines from within.'
Now think back, how long since you have seen one? Firefly sightings in urban areas are almost nil, and rare in rural pockets. The population of the magical glow worm is sadly declining worldwide. If proper attention is not paid to their conservation. In a few decades from now, they will be confined to books, fear ecologists.
According to Prof Amita Kanaujia of Lucknow University's zoology department: "Nothing brings back memories quite like the shimmering brightness of fireflies at dusk. However, there is a problem with these lovable, bioluminescent insects, sometimes referred to as lightning bugs. As the challenges against them mount, their populations are dropping globally. Experts claim that there are 18 species at risk of extinction in the United States alone. And surely, one would not want to live in a world where this experience is lost to one's grandchildren? One might not have to if one can do one's bit to ensure that fireflies will continue to light up backyards for generations to come."
Fireflies have been featured in human culture around the world for centuries. In Japan, the emergence of fireflies signifies the anticipated changing of the seasons. Firefly viewing is a special aesthetic pleasure of midsummer, celebrated in parks that exist for that one purpose. The Japanese sword called Hotarumaru, made in the 14th century, is so named for a legend that one night its flaws were repaired by fireflies.
Dr Nitin Kulkarni, director of ICFRE-Rain Forest Research Institute, Assam, said: "Fireflies, commonly known as lighting bugs, are a fascinating group of beetles active during dusk and night and communicate with their mates using light signals, known as bioluminescence. They are distributed in all tropical and temperate areas and prefer moist, marshy, and undisturbed habitats. Firefly larvae play an important ecological role as predators of soft-bodied invertebrates; whereas adults act as nocturnal pollinators of some plant species. Fireflies have economic importance in many countries due to the growing interest in firefly ecotourism. Despite the ecological and economic significance of fireflies, our efforts towards the conservation of fireflies are greatly neglected. Their population is declining due to anthropogenic or human activities such as the destruction and degradation of the habitats required to support the fireflies throughout their life cycle; artificial light that interferes with communication and mating (light pollution); injudicious use of broad-spectrum pesticides, excessive tourism, climate change-related drought and higher temperatures and overcollection and killing of fireflies. Indiscriminate use of insecticide reduces the firefly population by primarily killing the common food source for the firefly larva (the earthworms, slugs, and snails) and broad-spectrum herbicides destroy flora that fireflies depend on for shelter, food, overwintering, and mating. Modification of aquatic habitats of fireflies, such as dams and irrigation channels, can also negatively affect firefly populations.”
"Therefore, judicious efforts need to be directed towards the conservation of the fireflies which involves the creation, restoration, and protection of firefly habitats, i.e., by providing food sources such as nectar and pollen-abundant flowering plants, clean water sources, and providing undisturbed vegetation and underground burrows for overwintering larvae; minimizing the use of broad-spectrum pesticides and herbicides in firefly sensitive habitats; encouraging the use of selective pesticides in firefly habitats; reducing light pollution by unnecessary outdoors lighting, limiting the use of flash and floodlights during the active season of the fireflies and increase public awareness and educate community members regarding the conservation of fireflies," he added.
Why are glowworms important to the environment?
The decline of fireflies is not just the loss of a beloved natural spectacle. It causes broader ecological disruptions that could have cascading effects on other species and ecosystems. Fireflies serve as prey to some species and as predators for many invertebrates. So, they have a role in the food web. That is why it is feared that if they disappear there could be many repercussions on local biodiversity.
A green activist said on condition of anonymity: “Fireflies thrive in messy gardens with fallen tree logs and piles of dry leaves. However, such an ideal environment for fireflies is not to be found in urban sprawls, which are fast becoming concrete jungles. Elsewhere too, such habitats are declining due to human imprint and interference. Also, they are very sensitive to light. And not only are cities lit up all night long, but also villages are fast becoming electrified. So, naturally, they would be hard to find.”
All about fireflies
Fireflies belong to the Lampyridae family of elateroid beetles with more than 2,000 described species. Many of these species emit light. These insects glow at twilight, primarily to attract mates, so they are called fireflies, lightning bugs, or glowworms.
It is said light production in fireflies started as a warning signal that the larvae were distasteful. Then it became a mating signal and in a further development, adult female fireflies of the genus Photuris mimicked the flash of the Photinus beetle to trap their males as prey.
Fireflies are found all over the globe, save Antarctica, in temperate and tropical climates. They thrive in marshlands or in wet, wooded areas where their larvae have abundant sources of food. However, not all adult fireflies glow. All of them might glow as larvae, but only some as species produce light in the adult stage. The light organ's location may also vary among species and between sexes of the same species.
Since fireflies are beetles, they resemble other beetles in many ways, including life cycle and, undergo complete metamorphosis. Post mating a female firefly lays eggs on or just below the surface of the ground. The eggs hatch in three- or four weeks’ time.
In some firefly species with aquatic larvae, such as Aquatica leii, the female lays eggs on aquatic plants which have foliage out of water and the larvae go into the water after the eggs hatch.
Firefly larvae feed until the end of summer. Most fireflies hibernate as larvae, burrowing underground, or finding places on or under the bark of trees, only to come out in the spring. The larval stage can last from a few weeks to two or more years. The larvae of most species feed on other larvae, snails, and slugs. Some larvae have grooved mandibles that inject digestive fluids directly into their prey.
The larvae turn into pupa for one to two and a half weeks and then the adult firefly emerges.
The diet of an adult firefly varies according to species. Some feed on other insects or slugs and some on plants and pollen. Some adults, like the European glow-worm, have no mouth, emerging only to mate and lay eggs before dying. In most species, adults live for a few weeks in summer.
In general appearance, fireflies can vary widely with different colours, shapes, sizes, and even antennae. The size of an adult firefly depends on the species, and the largest can be up to 25 mm long. Non-flying larviform females are also found in many species. These can often be distinguished from the larvae only because the adult females have compound eyes, unlike the simple eyes of larvae. The females have much smaller eyes than those of their males.
Many firefly species are diurnal and do not emit light, but the most commonly known fireflies are nocturnal and the species that live in the dark emit light.
Most fireflies contain the steroid pyrones lucibufagins, which is quite similar to the cardiotonic bufadienolides found in some poisonous toads, so they are unsavoury for vertebrate predators. Interestingly, all fireflies glow as larvae
Light and chemical production
A chemical process called bioluminescence is responsible for the light emission in fireflies. There are specialized light-emitting organs, usually on a female firefly's lower abdomen, which produce light. The enzyme luciferase acts on luciferin, in the presence of magnesium ions, ATP, and oxygen to produce light. Firefly luciferase is used in forensics and the enzyme has medical uses, like detecting the presence of ATP or magnesium.
The light that the fireflies produce is "cold”, it has no infrared or ultraviolet frequencies. The light may be yellow, green, or pale red, with wavelengths from 510 to 670 nanometers. Some glow-worm species, like the "blue ghost" of the eastern US, may seem to emit blueish-white light from a distance and in low light but when observed closely, the light is bright green.
During a study on the genome of Aquatica leii, scientists discovered that two prominent genes were responsible for the formation, activation, and positioning of this firefly's light organ: Alabd-B and AlUnc-4. Adults emit light primarily for mate selection. They have several ways to communicate with mates in courtships, like steady glows, flashing, and the use of chemical signals unrelated to photic systems.
Some species show synchronization of flashing. Tropical fireflies routinely synchronise their flashes among large groups, particularly in southeast Asia. Glowworms synchronize their light emissions precisely along riverbanks in Malaysian forests. This is generally attributed to diet, social interaction, and altitude. In the Philippines, thousands of fireflies can be seen all year round in the town of Donsol. In the United States, one of the most famous sightings of fireflies blinking together takes place near Elkmont, Tennessee in June. The phenomenon is also seen in Congaree National Park in South Carolina.
Some species of fireflies do not emit light and are diurnal, or day-flying, such as Ellychnia. Some other diurnal fireflies that live in dark, shadowy places, such as beneath tall plants or trees, emit glow, like the specie Lucidota. Fireflies exist on every continent save Antarctica. Scientists believe there may be 2,400 species of fireflies with new ones being discovered. As the season winds down in autumn in North America, it begins or is underway somewhere else. The larval season is continuous everywhere. Yet some firefly populations face risks of survival. In North America alone, the Firefly Specialist Group of the International Union for Conservation of Nature (IUCN) has identified 18 species as “at risk of extinction.”
Prof Venkatesh Dutta, School of Environment Sciences, BBAU, Lucknow said: "Fireflies have disappeared from our neighbourhoods due to a combination of factors, including habitat loss, fragmentation, light pollution disrupting their bioluminescent communication and pesticides harming them directly or contaminating their food sources. Local climate change and heat have also severely altered their life cycles and habitats. Further, urbanization has led to habitat destruction and an increase in light pollution. Several invasive species are competing for resources, diseases, and parasites and a decline in insect populations, their primary food source. Human activities like fireworks and the burning of litter also disrupt their habitats. To conserve fireflies, it is essential to preserve natural habitats, reduce light pollution, use eco-friendly pesticides, support sustainable agriculture, and create firefly-friendly environments. By taking these steps, we can help protect these bioluminescent wonders and preserve their magical presence in our environment.
Threats to their survival
Firefly populations are thought to be declining worldwide. Though there is not much monitoring data for many regions, there are reports and several published studies from Europe and Asia suggesting that face fireflies are at risk. The recent IUCN Red List assessments for North American fireflies have identified species with heightened extinction risk in the US, with 18 taxa categorized as threatened with extinction. Habitat loss and degradation of forests and green cover, light pollution, use of pesticides, poor water quality, invasive species, over-collection, and climate change are some of the factors responsible for the dwindling population of fireflies.
The latest trend of firefly tourism, which is a growing sector of the travel and tourism industry, is also cited as a potential threat to fireflies and their habitats primarily because it is not managed suitably, with an eye on preserving the insect ecosystem. Land-use change (loss of habitat area and connectivity), which is identified as the main driver of biodiversity changes in terrestrial ecosystems, casts an adverse impact on fireflies just as it does on other organisms, animals, and birds. Pesticides, including insecticides and herbicides not only harm fireflies directly but also potentially reduce prey populations and degrade habitat.
Light pollution is a major threat to fireflies. Most firefly species are sensitive to environmental levels of light and consequently to light pollution. Studies on the effects of artificial light at night on fireflies have shown that light pollution can disrupt fireflies' courtship signals (bioluminescence) and even interfere with larval dispersal. Researchers and entomologists opine that it is necessary to protect and increase firefly habitat to conserve their populations. They recommend reducing or limiting the use of artificial light at night, restoring habitats where threatened species are found, and shunning pesticide use where not necessary, among many other things.
Dr Anuj Saxena, a retired IFS official, said: “Climate change, particularly large temperature variations, are the biggest adversary of glow-worms.” He cited a beetle garden he had seen abroad, where ideal conditions like optimum temperature, suitable vegetation etc. were made available in an airy enmeshed enclosure and suggested that on a similar pattern, suitable conditions could be created in existing sanctuaries for ‘firefly gardens’.
Firefly fests cause harm, say environmentalists
Of late there is quite a buzz about firefly fests, in India and several other countries. In Maharashtra, fireflies can be seen in dark spots in Lonavala, Naneghat, Purushwadi, Siddhagad Fort, Kothaligad Fort, Rajmachi Fireflies festival at Udhewadi, Bhandardara Dam, Harishchandragad Kalsubai Forest Area, Ghatghar Dam, Samrad Village and Igatpuri. Firefly festivals are also held at such locations and tourists flock to see the spectacle. Several other countries too hold such fests. While such entomotourism may have boosted rural economies, it has cast an adverse impact on the ecosystem as insect populations decline all over the world.
Small wonder environmentalists have vehemently opposed such fests, on the ground that tourists used flashlights, torchlights, and vehicle lights that caused light pollution and interfered with the natural mating process. They inadvertently crushed female fireflies while clicking photos, littered the area during the night camping in the forest area and often caught fireflies in bottles to take home as souvenirs, all of which caused great harm to the insect and disturbed wildlife in the forest.
What can be done?
According to Prof Amita Kannaujia, one should make a home for fireflies. She said the loss of habitats was now the largest danger to the species. “Although there are over 2,000 distinct species of firefly, they may survive in a broad range of habitats, such as marshes, woodlands, and even urban parks. For this reason, certain species are more vulnerable than others. Fireflies change into four phases of life: eggs, larvae, pupae, and adults, but despite this people often see them as adults. Fireflies spend the majority of these stages underground or in damp soil, where they may hunt for earthworms, which are one of their favourite foods. If one merely leaves some woody debris and leaf litter at the perimeter of one’s land or garden, you may easily reproduce those circumstances. One can also plant native shrubs and trees and let the grass grow long—all of which will help the soil retain the moisture that fireflies love.”
Switch off lights
Fireflies are particularly susceptible to the increase in light pollution because of the same glow that gives them their unique appearance. An essential component of the firefly mating ritual is the flashing of lights. Male fireflies hover about, signaling their attraction with flashes of light as the sun sets each night. When a female in the vicinity shows interest, she darts back from her ground-based perch, prompting the males to descend and locate her. It is far more difficult to perceive those indications in the city and suburban settings. According to a recent study, too much light at night, regardless of how dim, lowers the frequency of female reaction and the quantity of flashing among men. Thankfully, there are a few options. Any lights outside the house can have motion sensors, timers, or dimmers One can also draw the curtains at night to stop light coming in through the windows and, if feasible, turn off all the lights. Outdoor lighting and streetlamps with shielded coatings are also beneficial.
No pesticides, no fogging
Since fireflies are insects after all, spraying herbicides and insecticides can be fatal for them. Most pesticides for home gardens are broad-spectrum products. They kill firefly larvae just as they kill wasps, ants, and other less desirable insects. Alternatives to chemical insecticides that might target particular species, like mosquitoes, while sparing other insects, are being studied by scientists.
Adopt responsible firefly tourist practices
This may be a double-edged sword, as research has demonstrated since it can both disturb the life cycles and habitats of fireflies and promote respect for them. Watch where you walk when you visit areas where fireflies live to prevent stepping on the developing larvae or mating adults. Don't wander from elevated pathways intended to safeguard fireflies at firefly viewing locations. You might be able to carry a torch to these locations to aid in locating the ideal place to see fireflies. It's preferable to arrive early when it's still light outside so you don't need a torch at all. If you must, be sure to cover it with a dark red filter.
Fireflies are not just nature’s twinkling jewels. They are also an important indicator of a healthy ecosystem. If their dimming trend is to be checked, it is time to act and act fast, so that future generations continue to be enchanted by the show of living lights.
Leave a comment