Like moths to the flame
December 12, 2003 5:39 PM   Subscribe

If moths like lights so much, then why don't they come out during the day?

And don't say because they don't need to come out to get light.
posted by armoured-ant to Science & Nature (12 answers total)
Response by poster: Unless, er, that's why. See, I'm asking on behalf of someone else. Or something.
posted by armoured-ant at 5:46 PM on December 12, 2003

A wild guess: They are out during the day (I've seen moths in the day, though they seemed mostly dormant), but you don't see as many of them because they don't flock to you (because you have a light while most of nature is dark at night). Which does kind of raise the question if moths also attempt to fly to the moon.

Also: Do fireflies have moth stalkers?
posted by fvw at 5:46 PM on December 12, 2003

(as to why moths fly towards light: Howstuffworks is helpful as ever)
posted by fvw at 5:49 PM on December 12, 2003

I love this question : >

another wild guess: they're like bats somehow, or owls?
posted by amberglow at 5:50 PM on December 12, 2003

If I had to guess - and in fact, I will - then I would say that they come out at night because that's when the things they eat are active, too. I did some mad googling but couldn't find out anything related to moth-in-general night habits.

However I found out on this page that colorful moths are active by day and dull-colored ones are active at night, which in itself is kind of intriguing.
posted by contessa at 5:57 PM on December 12, 2003

Because if they came out during the day, they would try to fly at the sun? I don't know, but it's a good and interesting question.

Also, I've seen moths during the day, though I haven't found them flitting around light sources. So there goes the "don't come out during the day" truism.
posted by majick at 6:02 PM on December 12, 2003

hmm. i always thought the explanation was not that they aree trying to fly at the light source but around it.

To orient themselves during the day and fly in straight lines, see, they can just fly perpendicular to the rays of the sun.

At night, however, with a fixed light source, flying parallel to the light rays has you going, not straight, but in a path that takes you in circles around the light source. This explains why they dont actually fly directly at the light.

anways, i was told this once and it made perfect sense to me.
posted by vacapinta at 6:16 PM on December 12, 2003

sorry. change "flying paralell" to "flying perpendicular".

the sun of course is so far away that all its rays are for all practical purposes, just straight parallel lines so it makes a good source of orientation.
posted by vacapinta at 6:19 PM on December 12, 2003

Maybe they are too easy prey for birds? They come out, not when the things they eat are active, but when the things that eat them are not active. But that doesn't address why the colored ones can be active in the day.

What do moths eat, anyway?
posted by crunchburger at 6:55 PM on December 12, 2003

sweaters, no?
posted by amberglow at 7:09 PM on December 12, 2003

To reiterate fvw's link, it's not that moths "like lights so much," it's that they navigate via the moon, so humans are screwing up their sense of direction with artificial lights.
posted by hyperizer at 8:46 PM on December 12, 2003

Best answer: It looks like recent research indicates that the moon/sun navigation idea is probably not the reason nocturnal moths are attracted to light, and that we still don't really know what makes moths fly towards light sources. According to Cecil, though, Moth-man Henry Hsiao believes that the reason that moths stay circling the light is because of the "Mach effect", which makes the area just around a light source appear to be darker than the surrounding area, so really they are seeking the darkest part of the sky/room. Unfortunately, it looks like no real details of Hsiao's work are online, though he has published a book on the subject. (A bit of wikipedia on it here.)

The two main predators of moths are bats and birds, so nighttime moths avoid birds by avoiding daylight, and have ears that can detect bat sonar; most day-flying moths have camouflage coloration that hides them, or else, like the hummingbird moth or the clearwing moth, they mimic other species. Here's a nice page on how moths and butterflies protect themselves.

Crunchburger - moths eat leaves and flowers and drink nectar or sap.
posted by taz at 12:49 AM on December 13, 2003

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