Pursuit Problem and "bugs flying into flames"

I was researching the pursuit problem and found this cool bit of information at cut the knot .

Bugs fly into candles because of the design of their "flight planning" computers. Here is the goods:

Bugs determine a straight line by trying to maintain a constant angle with respect to a source of light, the natural one being sun. Now This works for distant sources of light such as the sun. But for sources of light closer by, the curve that satisfies the constant angle property is a logarithmic spiral. Well, its actually the same spiral all the time but when the source really far off, the spiral is well approximated by the straight line and, in fact, I suspect that fluctuations caused by movement of air is more significant in this case (than the infinitesimal angle change) and bugs might be wired to ignore small changes(even if their sensors could detect them).


Cool!