Entomology: Lifesaving Light

Light from a single, well-defined source holds such a strong attraction for night-flying moths that a flickering candle flame can lure them to a fiery death. But when light comes from all angles, as in a brightly lit room or outdoors during daylight, some moths cease all activity, as if they had been "turned off." Scientists have long wondered: What throws the switch?

In the current issue of Applied Optics, Entomologist Philip Callahan, of the Department of Agriculture, reports on delicate experiments with which he answered the question. Callahan caught some giant cecropia moths, which live in the woods, studied...

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