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I don't think it confirms that. It seems to be one of the popular theories they investigated. Later they say -

"In both field and lab conditions, insects rarely head directly towards, but consistently fly orthogonal to the light source. This refutes the fundamental premise of an escape response."

"An insect should keep a light source at a fixed visual location for maintaining its heading. Switching light position (Supplementary Fig. 5) shows that insects readily hold the light source on either side of the body."

It makes sense to me. Imagine you were an insect and you would use the moon for navigation. Would you really be flying directly towards moon? No, right? Then how could someone think that insects flying directly towards artificial light source is the basis for the theory that insects use moon as navigational aid?

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I think you're misunderstanding GP.

This definitely refutes the theory that insects are trying to escape towards the light, because, as the article shows, insects don't head directly for the light, but instead move orthogonal to it.

But this doesn't mean they can't use moonlight to help with flying. The theory, as I understand it, is that they use a distant light source -- e.g. the daytime sky -- to maintain altitude. There's no reason they couldn't use the moon to do this too.

Again, they would not be flying towards the moon, they'd be keeping the brightest light to their dorsal side. Since the moon is distant, unlike a lamp, this would result in steady flight.

I'm not sure that it confirms whether they use the moon or not, but it seems like a possibility.

Wait, so it could be a parallax thing?

The moon is in practical terms infinitely far away, and no matter how far the insect flies it won't budge and stay as a stationary feature to localize by.

But do the same with a lamp that's only 3 m away, and keeping it in the same spot can only mean flying around it in circles, towards, or away from it, otherwise it'll move around a lot relative to the insect observer.

The spiraling in might also be a kind of vertigo response as well. Normally the moon only goes up or down in your field of vision if you’re adjusting your angle - pitching or rolling. But an artificial light source moves up or downwards if you’re changing altitude but maintaining attitude. That would make flying up past the light ‘feel like’ pitching away from it, which might cause autonomic steering responses, similar to inner ear/visual conflicts causing humans to stagger and fall over.

Okay, something I'm confused about. "Dorsal side" means, as far as I can tell, your back. So if a fly is keeping its dorsal side facing the moon, that means its back is pointing at the moon.

When the moon's directly overhead, this makes lots of sense. Fly goes around wherever. But if the moon's low on the eastern horizon, would we expect flies to mostly be facing upwards, and mostly flying west?

Doesn’t it just make more sense that they orient their movement in relation to the moon? Doesn’t matter what the specific orientation is — if the moon is 3 inches across and sitting in a room, it’s gonna fuck with the insect’s navigation.

If your logic is "keep the brightest light source on your left", then for a light source that's nearby (as opposed to "infinitely" far away, like the moon) you'll end up orbiting it.

Depending on your precise navigation logic, you'll either end up with an increasing or decreasing orbit radius. If it decreases, you'll eventually crash into the light source.

> Imagine you were an insect and you would use the moon for navigation. Would you really be flying directly towards moon? No, right? Then how could someone think that insects flying directly towards artificial light source is the basis for the theory that insects use moon as navigational aid?

If you're flying parallel to the ground (horizontally), you'd want the moon to be where your back is and you'd have a good change of flying straight. It's like when the kids say that the moon seems to "follow" them.

"Dorsal" means where the top part is, the insect's back, as it were.

What’s so special about keeping it ‘where your back is’? The moon is rarely located directly overhead. Wherever it is, keeping it in a fixed relative position will get you going in a straight line.

The article talks about the ‘dorsal flight response’ being more about the overall alignment to the sky hemisphere, not the moon specifically.

“the brightest part of the visual field has been the sky, and thus it is a robust indicator of which way is up. This is true even at night, especially at short wavelengths (<450 nm)”

> What’s so special about keeping it ‘where your back is’?

Since we're to imagine the grandparent flying around like an insect. I imagined them as person flying but with insect wings. Since we're mammals with eyes pointing straight ahead, as opposed with them being on the side of our heads, we'd need some light sensor on our back to ensure we're flying straight at night and keeping the moon above, as opposed to having to look behind every so often to ensure the moon is still there :-)

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