Ever wonder why insects appear hopelessly attracted to lights at night in some sort of mesmerizing dance around our porch lamps and streetlights? This millennia-old mystery has finally found a new explanation, and it is not what we have always assumed.
Deep in the Costa Rican cloud forest, a team of scientists led by Yash Sondhi-a recent Ph.D. graduate from Florida International University-embarked on a nocturnal adventure. These insects’ 3-D flight paths were tracked by a research team of specialists from Imperial College London and the Council on International Educational Exchange in Monteverde, Costa Rica, with the use of a motion capture arena fitted with high-speed cameras and advanced technology. They found moths sporting wing spots resembling eyes, and shining armoured beetles, swarming around the light in hordes. What they found was a behavior that no one had ever recorded before: in flight, insects always kept their backs to an artificial light. They found all species observed flipped upside down when exposed to light, a behavior consistent with their findings in the wild.
As Sondhi explains, ‘Maybe when people notice it, like around their porchlights or a streetlamp, it looks like they are flying straight at it, but that’s not the case.’ The truth is, these insects have evolved over millions of years to navigate by using the brightest thing they know – the sky. But in our artificially lit world, they mistake these small light sources for their celestial guide.This phenomenon, now published in the journal Nature Communications, sheds light on a behavior that has puzzled humans for ages.
They are capable fliers-aerial acrobats at times-but their sense of gravity is unreliable during rapid acceleration, and thus the sky becomes a key reference point for control. Artificial lights seriously disrupt this system, leading to disoriented and often exhausted insects.
Funded partly by National Geographic, this study goes on to suggest that direction and type of light bear significantly on this disruption, especially upward-facing or unshielded bulbs. The results show the positive effects of shrouding or shielding lights to prevent negative impacts on insect populations.
But that is not the mystery in itself. Why insects are attracted from a large distance to light is still part of the mystery. It is only through the persistence of Sondhi, then getting the right team, that this discovery made a scientific breakthrough, underpinning the importance of persistence in scientific inquiry.
The present work constitutes a very important step in the study of the effects of our illuminated nights on the insect world and in taking measures for protection of these highly important creatures. Sometimes, to find answers to some ancient questions, it is enough just to take another look around or, more precisely, turning one’s back to light.
Funding was provided by the following agencies and organizations: the European Research Council; the National Science Foundation; the graduate school at Florida International University; the Susan Levine Foundation; the National Geographic Society; the American Philosophical Society; and the Tinker Foundation.
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Millennia-old mystery about insects and light at night gets new explanation
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Scientists think they’ve finally solved the millennia-old mystery of why bugs flock to your porch light
