Moths may be trapped in the light rather than drawn to it, according to findings that are highlighted in a recent study published in Nature Connections.
Moths and butterflies have been around for hundreds of millions of years. During this period, they may have adapted to turn their heads back towards the most luminous direction. The primary light sources were the Moon and stars, which ensured the flying insects knew their way up and maintained their flight level.
With the use of artificial lighting, moths began to incline their backs to streetlights at night. This caused them to form uninterrupted loops around the lampposts, relying on their evolutionary instincts mastered over millions of years.
Dr. Sam Fabian and his team at Imperial College London have used high-resolution, lab infrared motion capture and high-speed infrared video recordings to observe that moths and dragonflies turn their backs to light sources.
“If the light’s above them, they might start orbiting it, but if it’s behind them, they start tilting backwards and that can cause them to climb up and up until they stall…More dramatic is when they fly directly over a light. They flip themselves upside down, and that can lead to crashes. It really suggests that the moth is confused as to which way is up,” Fabian told The Guardian.
The study is the first to show this behavior in nighttime insects and suggests why moths are attracted to lights. It confirms that light pollution is a serious reason why insect numbers have decreased lately. Moths and other insects can get stuck in lights, making them quick food for, among other creatures, bats. Artificial light can also trick moths into thinking it is daytime, telling them it's time to fall asleep and not feed.
According to the authors of the research, the direction of light should be considered when planning and setting up outdoor lighting; it is advised to avoid an upward-facing light direction, as these are the most harmful for the insects.