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Why are bugs attracted to light?

It is often in the summer that people start to notice all the bugs circling around their porch lights and some coming towards their campfire.

There are a few theories about why bugs are attracted to light. One of the theories is that bugs go to light because they think other bugs will be there and are searching for food and/or a mate.

Another theory is that bugs go towards light because they think they will find flowers and flowers means there will probably be nectar. This is because some flowers give off ultraviolet radiation. There are some lightbulbs used that radiate small amounts of ultraviolet light and this ultraviolet light makes bugs think that they will be going to flowers.

A third theory is that bugs usually fly at night but when they see the artificial light source, they go towards the light source to fall into their daytime sleep.

One of the most popular theories has to do with a concept called phototaxis. Phototaxis describes how an organism moves according to light. If an organism is positively phototactic, it will move towards light (moths are a positively phototactic species) and an organism that is negatively phototactic will move away from light (cockroaches are a negatively phototactic species). Scientists do not really understand why some organisms are positively phototactic and others are negatively phototactic.

Some positively phototactic organisms use the natural sun or moon light to navigate — kind of how African Americans used the North Star in accordance with the Underground Railroad to escape. But, if a positively phototactic organism sees a lightbulb, it will mistake that for the moon and try to fly towards it. But that lightbulb is not the moon and so the bug ends up doing something it did not expect: It was able to reach the “moon.” So, the confused bug tries to reorient itself but it just ends up flying around in circles.

Which brings up the question: When the bug realizes this, why doesn’t it just fly away? To answer this, we must understand that there is one thing that bugs and humans have in common: We both have light sensors. Bugs have thousands of these sensors. When there is a really bright light, the sensors make it so that smaller amounts of light are taken in. In dim light, the opposite happens. It is hard for humans to see in the dark, especially right after we have seen a bright light. And with bugs, it takes them about 30 minutes to adjust to the darkness. If a bug ends up flying away from its light source, there is a chance that predators might come and attack the bug. So, the bug stays at the light source to avoid temporary blindness and thus, avoiding predators.

Bugs are usually attracted to UV light and white light. Try using yellow or red bug lights to keep bugs away. There are only a few bugs attracted to these lights but a large amount are attracted to white light. This is also why bug zappers work – they use white and UV light to attract bugs. But, using a repellent and setting up camp by the moon will be a lot more effective at keeping away bugs.

Bugs are usually most active during the summer and autumn. This is because the temperature and atmosphere during those two seasons is compatible with what bugs like. Most of the bugs disappear when winter comes (because it’s so cold). Most bugs (such as flies) die when they are completely frozen. This is true for most organisms on Earth because water expands as it freezes (it’s the only substance that does this) and this causes the ice crystals in the cells to rupture the cell membranes (outer lining of cell). Freeze-tolerant insects can be frozen and when they are thawed, they are still alive (kind of sounds like Aang from Avatar who can survive after being frozen in an iceberg for 100 years). The Antarctic midge Belgica antarctica can do this.

Vaageesha Das  is a sophomore at Morgantown High School. Today’s information comes from: Kanuckel, A. (2015, August 31). Why are bugs attracted to light? Farmers’ Almanac.