Turn on your porch light after sunset, and you will be treated to an aerial display by dozens, if not hundreds, of bugs. Artificial lights attract moths, flies, crane flies, mayflies, beetles, and all sorts of other insects. You may even find frogs and other insect predators hanging around your porch at night, taking advantage of the easy picking.
Unfortunately for the insects, their attraction to artificial light is a cruel trick caused by our innovation moving faster than their evolution. Night flying insects evolved to navigate by the light of the moon. By keeping the moon's reflected light at a constant angle, insects can maintain a steady flight path and a straight course.
Artificial lights obscure the natural moonlight, making it hard for insects to find their way. Light bulbs appear brighter and radiate their light in multiple directions. Once an insect flies close enough to a light bulb, it attempts to navigate by way of the artificial light, rather than the moon.
Since the light bulb radiates light on all sides, the insect simply cannot keep the light source at a constant angle, as it does with the moon. It attempts to navigate a straight path but ends up caught in an endless spiral dance around the bulb.
Mercury vapour lights are extremely effective at attracting night-flying insects, which is why entomologists use them to observe and capture specimens. Unfortunately, street lights that use mercury vapour bulbs also do an exceptionally good job of attracting insects. Incandescent bulbs also prove confusing to night-flying insects, as do compact fluorescent bulbs. If you want to reduce the impact of your outdoor artificial lights on insects, opt for either warm colour LED bulbs or yellow bulbs marketed specifically for reducing insect attraction.
Credits: Sabitha
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