The tiny shiny angels

When you walk out in the night you may have seen these blinking small lights all around your backyard, forming a wonderful and miraculous display. As you all know these luminous lights are generated by tiny insects called fireflies. But have you ever wondered how these lights are generated by these amazing tiny creatures? Or why do they do so?  

Fireflies are small insects in the group of beetles. There are no particular reports about number of species of fireflies from Sri Lanka, except the studies in colonial times. However, more than two thousand fireflies are found worldwide.  The first fireflies appeared 150 million years ago. These first fireflies did not have the ability to emit light. They used chemical sense to communicate and to locate mating partners. Even today there are some existing species which lives during day time and mainly depend on chemical senses and use their antennae the main chemical sensory organ to locate their mates. The ability to emit light which is known as the “bioluminescence” has been evolved independently from other groups that shows this biological phenomena. Scientists believe that at first this character was evolved as a warning sign for predators. In some species only females have the ability to emit light. These females are most of the times wingless and looks more like a worm. In Sinhalese known as “ra badulla”. They climb up to a higher place and emit light to attract males. But in some species both males and females can fly and emit light.

But how do they do this? In order to understand that we must go into molecular levels. There are three molecules responsible for this phenomena within the body of fireflies. Luciferin is a protein found in fireflies and many other animals with bioluminescence with slight differences in the molecular structure. Inside the body of the firefly this protein molecule is oxidized into oxyluciferin with the presence of Oxygen. This reaction is catalyzed by the enzyme known as luciferase and cofactors such as magnesium ions and ATP.

Energy released during this reaction is emitted as electromagnetic rays in the range of visible light. Thus we can see a light emission from the abdomen of fireflies.

Interestingly fireflies live most of their life in their larval form and all the larval fireflies have the ability to emit light even though their adults can’t. Therefore we can conclude that this character is primarily evolved for protection other than reproduction. However this character has been evolved as a useful tool in communication and mate attraction in adults. These adults have a very short lifespan where sole purpose of their adulthood is mating and laying eggs. Normally females tend to choose males with longer lasting flashes from their abdomen. As most of the insects their mating also may last for very long. They may stay attached to each other all night along. Another interesting phenomena the nuptial feeding is seen in many insects, can also be seen in fireflies. Male fireflies insert a fluid packed with proteins into female’s body which provide the energy required for the development of eggs within the female body.  

From where these molecules required for the production of light comes from? One possible explanation is that they produce these molecules inside their body. Yes that’s the truth for many species. However several species have lost the biochemical machinery required to produce these chemicals, but have evolved an even better behavioral adaptation to obtain these chemicals. Some female fireflies mimic the pheromone signals of other species and attract males of those species which have the ability to produce these proteins. Then they feed on these male fireflies and absorb these chemicals in to their body.

These creatures are predators that are very important in the balance and the persistent of an ecosystem. However with the increasing human encroachment in to natural habitats and due to various human activities these innocent animals are threatened largely. Habitat loss is one of the major threats for the survival of these animals. Light pollution is another most noticeable threat for fireflies as their main life style largely depend on the visual communication. Increasing white lights in cities are a huge problem for them. Use of light sources that these animals are less sensitive to is one of the main solutions when reducing the use of lights is less practical. So next time when you see a firefly lights in your backyard turn off the lights and let them experience their romantic moment in peace.

Tharaka Wijerathna