Lighting bugs

A fascinating study

by Firefly research group

W.M.C.D.Wijekoon, Dr. H.C.E.Wegiriya and Dr. C. N. L. Bogahawatte
Department of Zoology, University of Ruhuna.

Fireflies or “Lightning bugs” are the synonym given to this important group of insect. They are distributed worldwide with the greatest diversity of species occurring in the Oriental and the Neotropical regions of the world. Seven subfamilies inhabit in tropical and temperate regions.

The light emitting frequency and colour of light producing vary in different species of fireflies. In most firefly species both sexes have the flying ability, while in several species only the male can fly and the females are wingless and worm like, similar to their “larvae”. Though, they cannot fly, they have light emitting organs for searching food and mates in the dark

Two hundred and eighty species of fireflies have been recorded in Asia including 30 species from Sri Lanka. A reference firefly collection is also available in the National Museum, Colombo. If you are interested to see fireflies, you have to wait until 6.00 p.m. To ensure the best sightings of the visual displays of fireflies.

Their fascinating, automatically on, off light signalling pattern will be helpful to recognise even different individuals clearly at night. Studies revealed that they mostly inhabit in water associated open habitats and less visible in highly sheltered forest habitats.

However, after 8.00 p.m. they gradually move to tree tops to show their lightning behaviour to many members of their group. Definitely, the light emitting process is helpful to search their mates. So they can quickly find suitable partners in the dark and move towards them. It is indeed an elegant scene at night. Fireflies have their light emitting organ or “lantern” at the end of their abdomen. The male has two lanterns and the female has only one.

The light emitting frequency and colour of light producing vary in different species of fireflies. In most firefly species both sexes have the flying ability, while in several species only the male can fly and the females are wingless and worm like, similar to their “larvae”.

Though, they cannot fly, they have light emitting organs for searching food and mates in the dark.

These wormlike females and larvae are known as “glow worms”.

The well-known nocturnal crawler Re badulla is a real example for these wingless fireflies. There is a general belief among vegetable farmers in Sri Lanka, that fireflies are minor pests which feed on leaves of their crops. But, experts have discovered that, most adult fireflies do not feed at all.

They obtain energy during the larval stage and that energy is enough for the survival of the adult.

The firefly larva is a voracious predator, preying on snails, grubs, cutworms, and other soil-dwelling invertebrates. They inject their prey with neurotoxins and digestive enzymes that paralyze and break-down the body tissues, then consume the liquefied remains.

Fireflies play a significant ecological role in our environment. The number of lanterns are the main indicators of the sex.

Their light flashing behaviour, fireflies are increasingly studied for their use in night Zoos as an ecotourism subject. In addition, the bioluminescence in fireflies is being investigated thoroughly in the developed countries to find nanotechnological solutions to many unsolved problems, especially in medical sciences.

Their pulses of light represent a conspicuous signal that has been shown to function as an aposematic defense, which warns predators of distastefulness and unpallatability.

Several research studies have shown that ingesting fireflies can be lethal to lizards and frogs. In addition, fireflies are also important as general predators, feeding on insects and other invertebrates, some of them are well-known pests of various crops.

Fireflies are one of the least concern insect groups in Sri Lanka. Most of us have very poor knowledge about fireflies and their behaviour.

Even we have not updated our Taxonomic records on fireflies which were collected in the eighteenth century.

Since 2007, researchers of the Department of Zoology, and the University of Ruhuna have done some work on fireflies in Sri Lanka based on their taxonomy and ecology.

Apparently, fireflies in the world have threatened by various human activities on the environment.

Thus, we must renew the existing old but valuable information of fireflies in Sri Lanka, and conduct further research concerning their ecology and behavior for conservation of species threatened due to various anthropological activities.

As such, we must take steps today, to conserve this valuable group of insects.

We can conserve and learn about them by actively participating in public awareness programs, especially among the local community including school children and nature lovers.

Now is the time for scientists, naturalists and zoologists to spread their research work concerning this important group of insect in Sri Lanka.