What I'm struggling to understand is how the insects then reach so close to the artificial light. Why don't they spiral the artificial light from a great distance like 1 metre or 2 metres away? I see the insects hovering like millimetres or centimetres away from artificial light.
> 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.
https://news.ycombinator.com/item?id=39195508
Seems a reasonable explanation to me :)
The insects you see are the ones that happen to get too close and thus their nav gets 'jammed'.
It's similar to planes navigating by compass. Works great, until you go up to the arctic circle, then you better have another nav source or you too will be flying in circles.
Haven't seen flying insects since last summer but if I think they kind of lose altitude the closer they get to the light source, which would be when their torso is less horizontally oriented.
Also this is just a guess but I imagine the closer they're to the light source and the larger the contrast between bright and dark is, the stronger is their tendency to get locked into the orbiting path as opposed to flying randomly.