Nothing pronounces the arrival of summer like the flashes of fireflies
in the lawns and on the forest’s edge. Fireflies, or lighting bugs as
they are also known, are ‘charismatic’ animals – animals that are
noticeable, likeable and considered by many as ‘magical’ or ‘important.’
Fireflies are not flies, but beetles. With as many as 350,000 species
(or estimated to have up to 14 million total species) in the world,
beetles are one of the most specious groups of insects. Insects may
represent 90% of all life forms on earth.
Where do they live?
Fireflies are distributed mainly in the temperate and tropical regions of the world. Many live in marshes, near streams, or in wet, wooded areas. Adults are often observed by the edge of forests or in the lawns. Fireflies choose to live in these areas because these are where the larvae can find food (slugs and earthworms) and develop.
What is their lifecycle?
A lifecycle is a progression through a series of stages of development. Firefly lifecycle consists of egg, larva, pupa and adult stages. Metamorphosis is the process by which a firefly molts from one stage to the next. The older layer of exoskeleton is often left behind. Let’s start the lifecycle with the egg stage which usually lasts about 1 year. A few days after mating, a female lays her fertilized eggs on or just below the surface of the ground. Usually the female lays the eggs under some leaf litter or debris so to protect them from other predators. The eggs hatch 3-4 weeks later. The larvae are commonly called glowworms. The larvae of most species are specialized predators of other insect larvae, terrestrial snails, slugs, and earthworms. Some are so specialized that they have grooved mandibles which deliver digestive fluids directly to their prey. After several weeks of feeding, they become pupae, rest for 1 to 2.5 weeks, and emerge as adults. Fireflies overwinter during the larval stage. Some do this by burrowing underground, while others find places on or under the bark of trees. They emerge in the spring. Adult diet varies. Some are predatory, while others feed only on plant pollen or nectar.
Why do they flash?
Most fireflies are nocturnal – active during night time. So, their flashes are most noticeable at night. Fireflies flash to attract or respond to mates. Often, male fireflies will fly around in the dark and make very characteristic or distinctive flashes, as if saying ‘I am here! I am here!’ A female, which is often perched on grass or leaf, will make a single or multiple distinctive flashes in respond to the male’s flashes, as if saying ‘I am ready! I am here!’ The male will see the female’s flashes, come to the female and then mate with her. At any particular time, there are 4-5 species of fireflies active in one area. It is important to find your own species to mate, even in the dark. Some species, especially members of the genera Photinus, Photuris and Pyractomena, are distinguished by the unique courtship flash patterns emitted by flying males in search of females. See the section on ‘Identification’ for information on identifying firefly species or genera using flashing patterns.
How do they create flashes?
Light production in fireflies is due to a type of chemical reaction called bioluminescence. This process occurs in specialized light-emitting organs, usually on a firefly's lower abdomen. The enzyme luciferase acts on luciferin, in the presence of magnesium ions, ATP (adenosene triphosphate), and oxygen to produce light. Genes coding for these substances have been inserted into many different organisms. Luciferase is used in forensics, and the enzyme has medical uses. All fireflies glow as larvae. Bioluminescence serves a different function in larvae than it does in adults. It appears to be a warning signal to predators, since many firefly larvae contain chemicals that are distasteful or toxic. It is thought that light in adults beetles was originally used for similar warning purposes, but evolved for use in mate selection. Now fireflies are a classic example of an organism that uses bioluminescence for sexual signalling. They have evolved a variety of ways to communicate with mates in courtships. From steady glows, flashing, as well as the use of chemical signals unrelated to photic systems.