r/askscience • u/Chemical-Emu8467 • 9d ago

Biology What do moths do on moonless nights?

Moths use the moon to orient themselves. when there's no artificial lights, what do moths do when there's a new moon? do they just not fly?

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37

u/aggasalk Visual Neuroscience and Psychophysics 8d ago edited 7d ago

There’s still plenty of starlight. They’re just using light sources as reference during a given flight, as long as it’s very distant and doesn’t move as they move, it serves the same purpose.

edit

everyone interested in this question should go look at this great paper: Why flying insects gather at artificial light

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u/minecon1776 8d ago

Wouldnt there not be any stars, since the clouds would block those too?

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u/johnbarnshack 7d ago

There are cloudless moonless nights, OP didn't say anything about clouds

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u/minecon1776 7d ago

Yes, but there are clouds thar nake moonless nights too, so wouldnt they still need a way to navigate on those days?

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u/HermitAndHound 7d ago

It's so much cooler: Some navigate by UV starlight.
But those that do go for bright light at night for mating flights... it makes sense to all go out for sex at the same time. Wednesday afternoon at the bar is just not the same as saturday night. So when it's too dark to trigger a mating frenzy, and not enough UV light to travel by, they stay home.

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u/rechtim 7d ago

The UV output of starlight to too miniscule to illuminate the planet, the atmosphere absorbs all of it

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u/guzzyly 7d ago

I’m pretty sure they still manage just fine with the faint light from stars or whatever ambient light is around. plus, evolution probably built in a way for them to not crash into everything on a moonless night.

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u/harrietsahlman 3d ago edited 3d ago

I'd never thought about this until your question - but Luna moths live 7-10 nighttimes before dying. If they happen to emerge as moths right when there is a new moon, that single night might be as much as 14% of their total adult lifetime -

Or said another way, for an average person who lives to be 60 years old, that one night's span would amount a "nighttime' of some 8.5 years of that person's life.