Glowing scorpions and millipedes

(19 January 2018) Boys need toys… so when we encountered during one of our night walks two scientists spotting scorpions ‘playing with’ their UV torches, we had to get those as well. And yes, at the last walk two of us bought UV-torches. Let the game begin!
Scorpions, snail eggs, lichen and even millipedes galore: lots of living things can be detected in the rainforest at night, using UV-torches instead of normal light. So, what’s happening? First the correct terminology. Bioluminescent refers to light producing creatures, like some local mushrooms, fire flies and glow worms.

Fluorescent snail eggs

Fluorescence is different. Biofluorescence is the absorption of electromagnetic wavelengths from the visible light spectrum by fluorescent proteins in a living organism, and the reemission of that light at a lower energy level. Or, in normal language: it can’t be seen, unless one shines UV light on the creature. Chemical compounds in their exoskeleton absorb and re-emit ultraviolet light as visible light, which we humans can see. It’s now obvious why one never encounters a scorpion which is buying a UV-torch at Bunnings.
Humans can’t see UV-light, but most insects can. It helps them to find suitable shelter locations, away from the sun. It may also serve important functions in signaling and communication, mating, lures, camouflage, UV protection and antioxidation.
Biofluorescence is common among fish, spiders and scorpions.
During this night walk we also discovered fluorescent snail eggs and even a fluorescent millipede. We’re trying to find out more about that; I’ll keep you posted.
Last but not least: the Aussie budgerigars (the parrots) use fluorescent sexual signaling, with both males and females significantly preferring birds with the preferred fluorescent stimulus. Clearly, fluorescent plumage of parrots is not simply a by-product of pigmentation, but instead an adapted sexual signal.
Nevertheless, we did not attract any parrots to our torch this night – probably because they were asleep – but we did notice that many more insects like moths and mozzies are attracted to UV-light than to normal torch light: forewarned is forearmed.