A night sky of sparkling fireflies is truly magnificent. But have you ever wondered why, unlike other insects, fireflies glow? What makes them shine brightly? How do they do it?
Fireflies glow for the following reasons:
- To attract a mate. Glowing is a means of communication for fireflies. Male and females of the same species have distinct particular pattern of flashing light signals back and forth. They emit light at different intervals and glow at different wavelengths. During mating season, females just hang out on a tree branch or in the grass waiting for a mate. Males will then fly around, showing off their best flashes and doing their own pattern of signal. When a female recognizes the flash from a male of her own species, she will answer with her best flash also.
- To avoid predators. Glowing is also a means of warning predators to stay away from fireflies. These insects are filled with a chemical known as lucibufagens, which when ingested by predators will learn to associate the firefly’s glow with its bad taste. Hence, predators will think twice the next time they are tempted to swallow the glowing insects.
- To lure prey. Not all firefly species can produce lucibufagens. Thus, some fireflies eat other species that can make the chemical in order to acquire it. They accomplish this by mimicking the glow pattern of that other species and lure them in close. So when the unsuspecting male approaches, he does not become the mating partner but the instant dinner trait for the clever firefly.
- For survival of the species. The second and third reasons cited are also the fireflies’ means for their kind to continue their lifeline.
Now, the question of how fireflies glow remains unanswered. What’s in them that makes them emit light?
Fireflies, also called as lightning bugs, produce a green-yellow light which is a result of a chemical reaction happening inside the insect’s lower abdomen. The resulting light is called as “cold light” since it creates no infrared or ultraviolet rays. The chemical reaction involves:
- luciferin – a heat-resistant organic substrate which serves as the source of light
- luciferase – an enzyme that catalyzes the light-producing reaction. It is produced by the cells in the insect’s tail.
- oxygen – provides the fuel for the reaction to occur
The three elements combine to produce a chemical called oxyluciferin, and the process involved is called as bioluminescence.
Moreover, firefly larvae are also capable of bioluminescence. This is why they are also called as glow worms.
Anyway, fireflies are beetles, not flies!