They are attracted to lights
Hi. Insects that fly at night have evolved, over millions of years, to navigate using the moon. To an insect that is flying level with the ground, the moon will *always* appear to be overhead - slightly so, if on the horizon, to almost completely overhead. The moon also moves fairly slowly. Therefore, an insect flying at night that wishes to move in a relatively straight line has only one option: fly so that the relative position of the moon in their visual field stays constant. Can you imagine how this works?
Now, throw in human beings and their artificial light sources that are even brighter than the moon. When an insect is flying so as to keep the brightest light it sees in a constant relative position, and it sees a small, bright, artificial light, it will fly in a spiral or circle that, over time, gets closer and closer to that light source. So, insects that fly to lights at night usually fly around them in loops, circles, and spirals
· 1 decade ago