At this time of year if you are out and about on an evening stroll have a look in the undergrowth and see if you can spot a firefly. What makes this little insect so spectacular is bioluminescence – the ability to glow. Tamborine Mountain is home to the two most famous nocturnal, bio-luminescent creatures – fireflies and glow-worms.
Both species are insects with rather misleading names. The use and appearance of their bioluminescence is different, but the process that creates it is the same. A chemical reaction occurs between luciferin (a waste product), luciferase (an enzyme), and a reactant, in fireflies and glow-worms this is adenosine triphosphate (ATP) and oxygen. This chemical reaction produces energy in the form of light.
Fireflies are actually carnivorous beetles of the family Lampyridae. Although there are some 1700 species worldwide, only 16 have been described from Australia.
Eggs, larvae and adults all have luminous qualities, but the adults, particularly the males, emit the strongest light. The larvae are terrestrial and live in leaf litter, where they prey upon snails, slugs and earthworms. They can inject toxic digestive enzymes into their prey, which liquefies the flesh, allowing it to be easily consumed.
In spring the adult male beetles take flight and flash their white light signals as a mating display to the females, who remain on the ground. The females flash back a weaker signal to attract the flying males. The fireflies are able to regulate the emission of light by controlling the amount of air supplied to their cells. The ability to control light emission is dramatically demonstrated by some tropical firefly species, who gather together in trees and bushes, and synchronise their flashes in a spectacular light show.
Glow-worms are not worms, but the larvae of a mosquito like fly. There are only 3 species in Australia. Arachnaocampa flavus is the species endemic to Queensland, where it inhabits shady, protected places with high humidity, such as creek banks and damp rock faces.
Glow-worms build snares made of silk fibres, coated with beads of mucous. The snares consist of mucous tubes, in which the glow-worm resides, suspended below the tubes are long filaments coated with sticky beads of mucous, these “fishing lines” can be up to 40 cm in length.
When night falls, the glow-worms emit a pale blue-green light, which lures insects into the sticky threads of their trap. When an insect is caught the larvae reel it up using their mouth parts. The larvae live between 5-12 months and go through 4 moults. The adults flies live only a few days, they have no mouth parts and are unable to feed. They mate, lay eggs near the original colony and die. Once hatched, the young establish themselves in cracks and crevices, where they build their snares.
If you plan to observe glow-worms, avoid using insect repellent or shining torchlight onto the glow-worms, both can be damaging to them.
Even in these days, when we complain of light pollution, people remain fascinated by these little bio-luminescent creatures.