Ahh…summer! There's nothing quite like the warm weather to get you outdoors. The days are longer, so you can stay outside and play until almost bedtime. When the Sun finally sets, it's the perfect time to sit out on the porch to enjoy the cool breeze as the temperature begins to drop.
If you're like many kids, you might want to turn on the porch light and grab a book to read. Of course, you might not be able to sit out and read for very long if some unwelcome guests arrive. What are we talking about? The bugs attracted to the porch light, of course!
If you've ever spent much time outside after dark on a summer night, you've probably noticed how certain bugs are attracted to light, whether it's a porch light, a street light, or a campfire flame. Some bugs just seem to be drawn to and mesmerized by these lights. What's up with that?
Unfortunately, scientists haven't been able to pin down one simple explanation for this behavior in moths, flies, and many other insects. They have, however, developed several theories that might provide some insight into why certain insects seem to be attracted to lights.
A phenomenon called phototaxis explains how organisms respond to light with motion. Insects, such as moths, that move toward lights are considered positively phototactic. Other insects, such as cockroaches, that move away from lights are considered negatively phototactic.
One of the most popular theories holds that positively phototactic insects are drawn to lights because they act like a guide. Many insects find their way by keeping a natural light source, such as the Sun or the Moon, at a constant angle.
Unfortunately, when they encounter an artificial light, insects can become confused very easily. They may mistake the artificial light as the Sun or the Moon. Rather than keeping a constant angle with the Sun or the Moon, these insects instead begin to try to keep the artificial light at a constant angle.
Since the artificial light radiates light in all directions, however, insects can't keep the light at a constant angle. The usual result is that the insects will circle around and around the artificial light, which must be confusing and for them.
Scientists have also come up with a variety of other ideas that might explain insects' light-loving behavior. For example, some scientists believe artificial lights merely light a clear path for insects to follow. Rather than flying around in the dark trying to avoid obstacles, they instead head directly for lights because they can see that the path is clear.
Other scientists believe some insects may mistake artificial lights for flowers. How can that be? Scientists know that some flowers reflect ultraviolet light. To the extent that a particular artificial light also emits a small bit of ultraviolet light, some insects may mistake it for a flower, thinking it's a source of food!