Wednesday, 4 March 2015

Why are moths fatally attracted to light?

Saturday 28 February 2015

Moths are not attracted to light. They navigate by light, operating under the assumption that the main source of light is far, far away – ie, the moon. If, say, a moth keeps the moon always on its left-hand side, it will fly in a vaguely straight line for a fair while. (It's obviously more complicated than that, but the principle is the same.)

But if the light is a porch light, keeping that on its left-hand side will make the moth fly in circles (and we won't see it), in outward spirals (and we won't see it), or in inward spirals (and we will see it as flying 'towards the light').

This has worked out pretty well for them for 190,000,000 years, but in the past 50-75 years, man-made lights have made things occasionally confusing. Before that, the only thing that would confuse them would be rare small fires. (If a moth is in the middle of a forest fire, navigation is the least of its problems.) And again, even there, many of the confused moths would not be harmed, but would merely orbit in circles or outward spirals until the fire died out.

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