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The science of why insects gather around lights at night has never been nailed down. Popular theories propose that moths and other insects navigate (导航) by the moon and mistake lamps for moonlight, or that the insects fly towards light to escape coming danger. Now researchers believe they have a more convincing answer: contrary to current theories, insects are not attracted to light from far away, but become trapped if they fly close to an artificial light source.
According to Dr Sam Fabian, study co-author and Imperial College London entomologist, moths and many other insects that fly at night evolved to tilt (倾斜) their backs to wherever s brightest. For hundreds of millions of years, this was the sky rather than the ground. The rick told insects which way was up and ensured they flew level. But then came artificial lighting. Moths found themselves tilting their backs to street lamps. This caused them to circle around the lamps endlessly the insets trapped by their evolution.
Fabian and his colleagues filmed insect fight paths around lights in the lab. The videos reveal that time and again, moths and dragonflies turned their backs to artificial lights. which appeared to greatly change their fight paths. " If the light is above them, they might start orbiting it, but if it' s behind them, they start tilting backwards and end up flying in circles or diving toward the ground.
Researchers have long waned that light pollution is a big driving force in the dramatic decline in insect populations. Moths and other insects that become tapped around lamps, become easily caught by bats. The artificial lighting can also fool them into thinking it is daytime, causing them to bed down and skip a night' s feeding.
There are, Fabian believes, helpful lessons from the research. " What this tells us is that the direction of artificial light matters. Could we change lighting environments to not trap insects? For we're facing a massive decline in insects around world, and artificial light at night is one of the factors that could potentially be leading to this decline. " Fabian said.
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