Search for twinkling stars on the Earth

INTRODUCTION

Fireflies’, ‘glow worms’, and ‘lightning bugs’ are quite common insects for us. They are actually beetles that belong to the family Lampyridae. There are around 2,000 species of fireflies all over the globe. In India, only 7-8 species can be found. These beautiful tiny creatures are easily visible during their mating season in the months of May and June in India. These insects can be found in the marshy and woodland areas where their larvae get plenty of food to survive. Though fireflies are renowned as nocturnal species, many are diurnal, like the ones in the genus Ellychnia. They are unable to produce light and depend on pheromones to get their mate. Some fireflies use both pheromones and bioluminescence in their sexual signals.

After mating, eggs are laid on or under the soil. Larvae come out within three to four weeks of egg laying. These larvae are ferocious predators. They hunt on various species of snails, slugs, and even larvae of other firefly species. They insert a numbing fluid to kill their prey. Some larvae also live on pollen and nectar. Astonishingly, they spend the whole winter hibernating under the soil or within the tree bark. Fireflies produce bioluminescence with the help of an enzyme ‘Luciferase’. Luciferase reacts with a chemical compound named ‘Luciferin’, oxygen, calcium, magnesium, and adenosine triphosphate (ATP) to produce light. This light is ‘cold light’ as it doesn’t produce heat unlike other light sources (Scientific American, 2005).

Bioluminescence in fireflies serves different purposes in different phases of the life cycle. In the larval stage, photic emission is used as a warning signal which helps to protect themselves from their predators. Whereas, in the adult stage, the photic signal is used in mate choice. Different firefly species have their unique flash pattern. This property is sometimes exploited by Photuris females. They mimic response flashes produced by Photinus females and ultimately hunt down and consume the approaching Photinus male (Lewis et al., 2012). There are some south-east Asian firefly species who exhibit synchronized flashing behavior.

FIREFLY AND ECOSYSTEM

Fireflies control the delicate balance of the ecosystem by controlling pests like snails. Fireflies like moist and humid places. Even in dry areas, they look for moisture. This way they indicate the presence of water (National Geographic, n.d.).

WHY ARE THEY BECOMING EXTINCT?

We all agree that fireflies are not easily visible nowadays. The number of fireflies has decreased drastically in the last few decades. A study conducted in 2019 (Chatragadda, 2020) in Tamil Nadu based National Centre for Coastal Research (NCCR) identified a drastic decline in the population density of the fireflies in Barrankula village of Andhra Pradesh. This comparative study showed that more than 500 fireflies found in 10 square meter area in 1996, reduced to 10-20 fireflies per 10 square meter in 2019. Our negligence has pushed these beautiful creatures towards extinction. The result of a global survey published recently (Lewis et al., 2020) found out the following factors associated with the declining firefly populations.

1. Loss of habitat : It’s easy to realize now temperature and moisture play important roles in the life cycle of fireflies. Like many other threatened species, loss of natural habitat is the main reason for their unavailability. Random urbanization and industrialization are grabbing lands causing the loss of habitats of fireflies. Unplanned agriculture is another threat to their habitat.

2. Light Pollution : This is also a vital cause of the disappearance of fireflies. Photic emission plays important role in the reproduction of these beautiful creatures. The Lower part of the male’s abdomen produces light that attracts females. Duration of flash plays important role in fireflies’ courtship which is being disturbed by unnecessary use of lights in agriculture and human habitation. Some fireflies even use light signals to get their food. They are also being affected by this. From satellite imagery, we can observe that human habitations are becoming brighter at night, day by day. Purushwadi, Rajamachi, Bhandardarathese villages of Maharashtra are famous for firefly festivals. Lots of tourists gather to watch thousands of fireflies in the pre-monsoon months, which is the peak breeding period of fireflies. The use of torch lights and flash photography is creating trouble for them there as well.

3. Use of Pesticides : We all are aware of the effects of chemical pesticides on nature. Toxic pesticides are getting mixed with soil and water nearby agricultural fields. Larvae of fireflies remain under soil or underwater for a long time of their life cycle and thereby get harmed. Agricultural insecticides such as organophosphates and neonicotinoids are also causing damage to fireflies. Unscientific and excessive use of pesticides accelerating this process.

Apart from these factors, water pollution, climate change, invasive species, tourism, and overharvesting of fireflies from nature are the other major threats to fireflies.

CONSERVATION

Firefly conservation has not become familiar to us until recently. In 2018, IUCN formed the Firefly Specialist Group (FSG) with the vision to study 2000 species of fireflies over the globe. This team has 26 members from 6 countries. Although we should have come forward much earlier to save these stars on Earth, it is still not too late. We can reduce water pollution, unnecessary use of lights, and pesticides. The usage of green pesticides may be effective to protect them. We also need to protect their natural habitat. Firefly festivals can be done, but tourists should become more conscious and responsible. Finally, more extensive research needs to be carried out on fireflies. Otherwise, we as well as the future generations will miss the magical nights of summer.

REFERENCES

1) SCIENTIFIC AMERICAN. (2005, September 5). How and why do fireflies light up?. Retrieved on October 10, 2020 from https://www.scientificamerican.com/article/how-and-why-do-fireflies/

2) Lewis, S. M., Faust, L., & De Cock, R. (2012). The Dark Side of the Light Show: Predators of Fireflies in the Great Smoky Mountains. Psyche, 2012, 634027. https://doi.org/10.1155/2012/634027

3) National Geographic. (n.d.). Fireflies. Retrieved on October 10, 2020 from https://www.nationalgeographic.com/animals/invertebrates/group/fireflies/

4) Chatragadda, R. (2020). Decline of luminous firefly Abscondita chinensis population in Barrankula, Andhra Pradesh, India. International Journal of Tropical Insect Science, 40(2), 461–465. https://doi.org/10.1007/s42690-019-00078-7

5) Lewis, S. M., Wong, C. H., Owens, A. C. S., Fallon, C., Jepsen, S., Thancharoen, A., … Reed, J. M. (2020). A Global Perspective on Firefly Extinction Threats. BioScience, 70(2), 157–167. https://doi.org/10.1093/biosci/biz157