I am staying in Landour, Mussoorie since last two years , but I didnt observe any firefly species in the area. Local people also told me that they have also not seen fireflies in the area. This was in line with the global trend of disappearance, or migration, of these fascinating creatures. But, this year in the month of July-August, I witnessed a sudden appearance of these lighting insects in Landour. They were seen in Pine and Oak forest patches near Woodstock school in the evening. I found them hovering around moth maple trees around midnight. And this led me to probe these magical bugs.
Fireflies are unique because they produce their signature glow through light organs located under their abdomen. They take in oxygen within special cells and combine it with a compound called luciferin to produce light with almost no heat. This type of light production is called bioluminescence, and this unique species account for 40 per cent of all insect species in the world.
Fireflies are, in fact, beetles— belonging to the Coleoptera order of the Lampyridae family— that have existed in our planet since the dinosaur era, says Sarah Lower, an evolutionary geneticist at Bucknell University, Pennsylvania, USA. There are over 2,000 species of fireflies across the world and they mark their presence in all continents, except Antarctica. In India, fireflies are known as Jugnoo in Hindi, Jonaki Poka in Bengali and Jonaki Porua in Assamese. These nocturnal insects are winged, which distinguishes them from other luminescent insects of the same family.
Firefly behaviour reveals that each blinking pattern is an optical signal to find potential mates. But when predators such as lizards attack, they produce drops of blood that are filled with poisonous chemicals. Significantly, fireflies are indicators of a healthy environment. They are extremely sensitive to changing environmental conditions and thrive only in healthy habitats— where the water is free from toxic chemicals; where the land diverse enough to support different life stages of fireflies; and, where there is minimal light pollution. Fireflies—mainly feeding on pollen and nectar—also play a vital role in pollination and the propagation of many plants.
At the same time, their larvae consumes invertebrate pests like worms, snails and slugs. In fact, some scientists have gone to the extent of using the luminesce property of fireflies to detect cancer and other diseases. For instance, Swiss researchers took the protein that makes fireflies glow and added a chemical tag to it, so when it attaches to another molecule—like on a tumour cell—it will glow. The study was published in Nature Communications in 2015.
“Everyone is reporting declines in their populations,” says Eric Lee-Mäder, co director of the pollinator program, Xerces Society for Invertebrate Conservation, a US-based non-profit. “I have observed a drastic decline in firefly population in the campus of the Wildlife Institute of India (WII), Dehradun, since 1999,” says V P Uniyal, senior scientist, WII. Though the exact extent of the decline is not known, reports suggest that their numbers have either shrunk or disappeared in many places, or they are migrating to find new habitats—moist, humid, wet or damp regions. Population declines of fireflies are due to various factors, including loss of habitat due to rapid urbanization and deforestation and light pollution that prevent fireflies from seeing each other’s flashes, thus indirectly affecting their biological cycles as they are unable to find their mates. A study published in Ecology and Evolution in 2018 says light can make fireflies lose track of time or their position or even blind them. Besides, there is the threat of pesticides—a large part of a firefly’s life is spent as a larva, on or under the ground, or underwater where they are exposed to pesticides.
Fireflies are also signalling the impacts of a changing climate. A number of reports suggest with changes in the global climatic conditions, the ecological habitat and distribution of the fireflies are also changing. That could be the reason for the appearance in Landour, where fireflies have extended their duration of stay. Here, summers have become comparatively warmer along with extreme rainfall—from April to September. The changing climatic conditions may have driven fireflies to migrate and extend their distribution to this part of the lesser Himalayas.
A 12-year study published in Science in 2016 found that warmer springs caused by climate change would led to early firefly peak, but only if rainfall remains the same. On the flip side, the seemingly increase in the number of firefly in other regions may be due to wet springs—a trend occurring with climate change in the northeastern USA, says Michael Hoffman, professor emeritus, entomology, Cornell University.
I have come across many studies that have focused on the biology and luminescence of fireflies, but there is little research on the global effects of climate change on firefly ecology and habitat. The disappearance of fireflies comes amid a larger decline in insect populations globally. This will leave the world with more pests and fewer pollinators both of which will threaten food supplies—and less luminance and wonder.
*The article is published in Down to Earth magazine October (1-15) issue
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