“We were just standing here talking, and suddenly he fell over!”
Why does the moth love the flame?
You turn on the porch light and there they are, banging their little moth noggins against the lightbulb, desperate to break through and be consumed in flames. There doesn’t seem to be a good evolutionary explanation for this, but there they are, doing it, all night long. Why?
Well, one explanation is that a moth’s navigation system depends on transverse orientation, keeping a fixed angle on a distant source of light — typically the moon, apparently. So the moth is trying to keep the moon in a fixed place, and then along comes your porch light, and the moth gets all confused, ending up in a spin around the bulb. Or maybe not. It’s possible that people just made up the concept of “transverse orientation” in order to explain the moths, and it doesn’t really make a whole lot of sense. Why couldn’t moths just fly in whatever direction they wanted to fly, like everybody else?
There’s another possible explanation, which is that female moths’ pheromones are slightly luminescent, and emit some of the same frequencies as candlelight, so the moths trying to immolate themselves think they’ve found a spectacularly turned-on lady moth. Except moths are even more attracted to UV light than candlelight, and UV light doesn’t have the same wavelengths as the pheromones, so that’s not it either.
People also use the word “phototaxis” to explain this phenomenon, which once again doesn’t really apply to anything except moths, and another possibility is that flowers reflect UV light, so maybe the moths think that the lightbulbs are a food source. There’s a point at which this is more about you than the moths.
Dark Shadows Every Day 