It’s a common phenomenon in Northeast Pennsylvania and other parts of the world—insects like moths are naturally drawn to light. You’ve likely seen this behavior firsthand if you’ve spent any time outdoors at night.
Maybe you’ve wondered why insects are attracted to light. This is known as positive phototaxis in the science community. Cockroaches, for instance, scatter when a light is turned on. This makes them negatively phototactic.
The short answer is—no one is 100 percent sure why this happens; however, scientists have developed a few popular theories.
One theory states bugs are attracted to light because they are looking for food. Therefore, they prey on other insects flying near light bulbs and other sources of light. Another possibility is the presence of light tells insects there are no predators nearby.
A predator would block the light, a clear sign of danger. Some scientists believe insects are drawn to a lightbulb as a heat source. It gets cool at night, and bulbs give off some heat. Bugs may be flying around lights to keep warm. Another more widely-accepted theory has to do with how insects fly.
What is it about light that attracts insects?
One of the most common theories focuses on light as a navigational system. Insects normally see three kinds of light: ultraviolet (UV), blue, and green. UV light signals open space to insects. (The sun and the sky are the only natural UV light sources; flower petals reflect ultraviolet light.
Closer to home, some light bulbs give off a small amount of UV light; bug zappers utilize UV light to draw insects. Insects are unable to tell the difference between natural and artificial light and simply follow the glow. Most insects are drawn to the white incandescent, white fluorescent, or mercury vapor bulbs found in standard streetlights, which is why it’s not unusual to see dozens of these insects circling a streetlight at night.
Insects typically use natural light sources (i.e., moonlight) as a guide while they fly. However, artificial light sources, such as porch lights, trick the insects. Bugs are drawn to the light, thinking it’s the moon.
The bright lights of a porch, streetlamp, or outdoor security light confuse the insects further. Light bulbs are considerably brighter and shine in more directions than standard moonlight. A moth flies in a relatively straight line when flying by moonlight because the moonlight stays at a consistent angle. When drawn to the artificial light, an insect gets confused and disoriented by the light shining at different angles, so it flies in circles.
Another theory developed by an entomologist in the 1970s said male moths were drawn to candlelight because the candle’s flame gives off some of the same frequencies as female moths’ pheromones. (This theory has been disproven).
Why do bugs go-to light at night?
Moths and other nocturnal insects are used to navigating their flight path by moonlight. With the advent of artificial lights, such as electric streetlights, porch and other outdoor lighting on peoples’ homes, there is far more light at night to attract bugs. This abundance of light also means bugs are confused more easily, as well.
Are all bugs attracted to light?
Moths are best known for being drawn to light. However, other insects like flies, crane flies, mayflies, and beetles also fly toward light. Sometimes smaller animals that eat insects, like frogs or spiders, can also be seen near lights looking for food.
Some scientists say the abundance of artificial light, or light pollution, negatively affects some insect species. For example, fireflies have difficulty telling the difference between natural and artificial light.
Certain moths only live for a few weeks and may spend most of that time circling a streetlight rather than reproducing. Other scientists have noticed mayflies are drawn to light from their homes in ponds and other bodies of water. Like moths, the mayflies get distracted by the light and focus on this rather than laying eggs.
For homeowners looking to lessen the impact of insects flying around your outdoor artificial lighting, consider changing the bulbs in your porch or other outside light. Warm color LED bulbs or bulbs meant specifically to reduce insect attraction are a better option. These bulbs can help minimize the number of insects flying around your outdoor space and prolong insects’ lifespans.
You don’t want the insects drawn to your outdoor lighting to become a problem inside your house by way of doors or windows. If nocturnal pests are becoming a problem when you’re trying to enjoy the great outdoors, try a bug zapper. Or contact a pest control professional below for more tips and advice on controlling the insect population in your home or around your property.
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