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Caught in the light

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Mark Carwardine Mark Carwardine | 17:57 UK time, Wednesday, 9 January 2008

From: Tefe
Mark is mesmerised by the millions of bugs lit up by the street light.

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  • 1. At 01:06am on 23 Oct 2008, cedgray wrote:

    It's an interesting behaviour that moths have around lights. They're not actually attracted *to* them as such - or at least this is the theory I've heard...

    When flying at night, evolution has adapted their eyesight to be aware of the second-to-second immovability of the moon in the sky: when it stays in one place, they know they're flying in a straight line.

    When faced with an alternative, modern-day light source of considerably increased brightness, they treat it as a 'super-moon', but it has a peculiar effect on them, due to the fact that it's close-by and changes its apparent position as they fly.

    Because this fake moon seems to move across their vision, their navigation equipment is telling them that they must be travelling in a curve: exactly the path that would make the real, distant moon swerve across their visual field as the street light is doing, and they therefore attempt to compensate for it by turning to keep it in the same place.

    This makes them loop about madly, trying to keep their 'moon' in one place, in a vain attempt to keep flying 'straight'.

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