Why fireflies first started to glow during flight
Adult fireflies evolved their glow to attract mates, not to ward off predators1.
Today’s mature fireflies (family Lampyridae) illuminate the sky primarily for courtship. But research suggests their flashy properties are also a stay-away signal, warning a predator not to expect a tasty treat. Scientists have long debated which purpose sparked the evolution of the beetle’s aerial glow.
Gareth Powell at Brigham Young University in Provo, Utah, and his colleagues examined the evolutionary histories of fireflies and their luminescent relative, click beetles (family Elateridae). Extrapolating from eight beetle fossils with known ages, the authors estimated when other species arose. They then built a firefly family tree that suggested an origin date for the insect’s bioluminescence.
They determined that fireflies and click beetles began lighting up the air about 133 million and 105 million years ago, respectively. These ages suggest that the insects glowed long before their current aerial predators ― bats and birds ― existed. Because adult fireflies began twinkling before flying animals posed a threat, the authors infer that their luminescence evolved as a sexual signal.
doi: https://doi.org/10.1038/d41586-022-01966-8
References
1. Powell, G. S. et al. Proc. R. Soc. B https://doi.org/10.1098/rspb.2022.0821 (2022).
