Why are moths drawn to light?

This might be interesting:
http://www.straightdope.com/classics/a5_038.html
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Moths cannot focus on anything more than a few feet away. Any light at a distance registers as a vague area in the field of view. And trees or shrubbery more than a few feet away register as vague, dark splotches - not sticks and leaves.

So the "beeline" toward a light as a tendency to fly toward the open space, rather than smack into the nearest tree or predator-inhabited shrubbery, seems likely. So far so good.

But that won't do for distance flights. Moths that fly fair distances need some kind of "constant angle on distant thing" to keep from circling - unless prevented, any moving animal will circle. And moth collectors know that many fewer moths turn up at lights if the moon is up and bright.

Not all moths fly for distance.

Not all moths fly to light with enthusiasm, either. The tendency varies by taxonomic classification, even down to species.

The experiment with the little boats does not completely convince me, especially its conclusion that moths do not spiral in - I've seen some moths spiral in. Not all.

And the Mach band explanation is an elaboration that does not replace: I've also seen moths - and June bugs, mayflies, etc, - spiral or even "beeline" directly into a light, and bounce off it. And afterwards some act simply dazzled - their navigational systems fried, temporarily.

But, from the moth's point of view: a dark place near a light place is very likely a goal of many moths. It would be a hiding place near the edge of a clearing, in the pre-bulb world, and a marked gathering place any other moth could find - get into pheromone range. And we who have hunted moths at streetlights know that many, especially certain kinds, land out around the rim of the lit area. So the Mach band could be more than simply an optical illusion kicking in at the one foot range - it may be the goal of the spiral from a longer distance.

So from my experience, I would say that different kinds of moths have different navigational needs, and a couple of different navigating strategies will carry a moth into a bright light and bang its head on the windiow.
 
spidergoat said:
Nope, none of you are correct. Moths go towards light because of their instinct to fly out of a confined space. Confined spaces are darker, and the opening is usually lighter.
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I like this one too. Occam's razor. But I also like this one for pretty much the opposite reason:
University of North Carolina medical technologist Henry Hsiao put forth an interesting theory concerning the Mach Band, an optical illusion well known to painters, where a harsh line between darkness and light produces an apparition of two bands, one light and one dark. Hsiao asserted that moths fly into the dark Mach band in an attempt to evade the light, which puts them into orbit around a terrestrial light source—a marvelously creative explanation. To my mind, the most logical hypothesis posits that moths fly perpendicular to light radiation. Under a normal night sky, this keeps them flying horizontally, but will cause them to circle about a candle if that is the brightest light source.
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That second one sounds so esoteric it must be true.
 
To my mind, the most logical hypothesis posits that moths fly perpendicular to light radiation. Under a normal night sky, this keeps them flying horizontally, but will cause them to circle about a candle if that is the brightest light source. ”

That second one sounds so esoteric it must be true.
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Under a normal night sky, flying perpendicular (on the vertical axis) to the brightest sky would send them into the ground. Or high into the air.

More moths come to lights on dark, cloudy, warm, calm, high-humidity nights.

Moths that need to fly long distances without circling have to be navigating differently than moths that need to find a nearby place to mate or feed.

Lots of other insects come to lights. Birds hit lighted windows, migrating at night.
 
Why are moths drawn to light?
They wanna feel warmer.

Do you see any moths in the winter?
 
Yes. Hence why I hate august. They get obcessed with coming inside. Within days I've got about 15 flies trying to come in, a spider and a moth. Arrrgh... :bugeye:
 
Hapsburg said:
Good point. I rarely see insects outside in the winter or even mid-late autumn. They're usually trying to get inside my warm house, the freeloaders.
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Damned social parasites.
We should have them all deported!
 
Do you see any moths in the winter?
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You do, certain Geometrids - the air temp has to be well over 40F, AFAIK, but they'll fly out over the snow in January in Minnesota on sunny days.

Those moths, again AFAIK, don't come to lights. If you want to cathc them, you sugar for them.
 
TruthSeeker said:
Those moths are different then those attracted to light...
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That may be but the fact that moths either die in winter or hibernate during winter hardly proofs that they are attracted to lights because it gives them warmth.
 
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