Fireflies, one of the most conspicuous of nocturnal insects, are a relatively recent addition to the twilight world. A new analysis of all bioluminescent species suggests that those living on land might be mere tens of millions of years old – a fraction of the age of bioluminescing marine groups. Bioluminescence serves many purposes, from communication to finding mates, scaring off predators to attracting prey. Yet while many marine species bioluminesce, very few terrestrial animals have evolved the ability. Besides fireflies and a few other insects, only one snail, a few earthworms and a handful of millipedes can produce light.
Most marine light-producing animals can trace their origins back to the Devonian period, at least 400 million years ago, wheres bioluminescent animals are all much younger – no more than 65 million years old. It's possible that luminescent species appeared on land only when night life began to diversify, although there are indications that some of the dinosaurs and early birds living before the bioluminescent insects evolved were already nocturnal. Another possibility is that terrestrial species have only recently cracked the problem of disposing of the toxic by-products of bioluminescence – less of an issue in the marine realm where temperatures are often cooler and more stable than in tropical forests.
Whatever the reason for the discrepancy, the future for terrestrial bioluminescent species might not be bright. While bioluminescent insects on land have diversified into 13 known species, most of them are known from only a single collected individual. That suggests they are extremely rare and vulnerable to extinction.
Via Dr. Stefan Gruenwald