Have you ever wondered why bugs seem to always swarm around light sources? The reason why insects are attracted to light has puzzled scientists for many years. There are a variety of theories available – all of them pretty sad…
What is Phototaxis?
The scientific term for an organism’s attraction to light is “phototaxis.” Phototaxis is a behavior exhibited by many bugs, including moths, beetles, and flies. It is the reason why these insects are often found hovering around light bulbs, lamps, and other light sources. This behavior is believed to be triggered by the insect’s eyes, which are specially adapted to detect light. When a bug detects light, it will move towards it. But why?
Does attraction to the moon and stars explain why insects are attracted to light?
One theory proposes the reason why insects are drawn to light is that they use it for navigation. Many insects use the moon and stars to navigate, and when they see an artificial light source, they mistake it for the moon or stars and fly towards it. They then try to fly towards the light, but because it is so close, they end up flying in circles around it. Sadly, the light source is leading the insects astray.
The problem with this theory is – insects don’t normally fly towards the moon or stars.
Ultraviolet light attracts insects
Another reason it is theorized that insects are attracted to light is that many light sources emit ultraviolet (UV) light. Insects can see UV light, and some species use it to find food and mates. For example, flowers often have UV patterns on them that guide bees to the nectar. Insects mistake artificial light for natural sources of UV light and are drawn to it. This is why many bug zappers use UV light to attract insects. Once the insect is attracted to the light, it flies towards it and is brutally electrocuted (ouch).
Attraction to heat may explain why insects are attracted to light
Another theory proposes some insects are attracted to light because of the heat that lights emit. Insects are cold-blooded creatures, and they rely on their environment to regulate their body temperature. When they sense heat from a light source, they are drawn to it because it can help them warm up. This would explain why some insects, like moths and beetles, are often found hovering around light bulbs. The warmth from the bulb can help regulate their body temperature, especially on cool nights.
Determine direction to the sky
A new theory has arisen in the entomology field regarding the behavior of insects around artificial lights at night. Biologists Samuel Fabian from Imperial College London and Yash Sondhi from Florida International University led a team that proposed that when many insects see bright lights at night, they believe they have found the direction of the sky and attempt to orient themselves along an up-and-down axis. This prompts them to roll their backs toward the light, which can cause them to go into endless banking turns like a tiny airplane or to crash-land, especially if the source of light is on the ground or mounted horizontally. Lights at night appear to hijack the directional instincts that help flying insects stay level by keeping their backs pointed toward sunlight during aerial maneuvers in the daytime.
To arrive at this conclusion, the scientists recorded high-speed, low-light video of dragonflies, butterflies, and moths flying around light bulbs both in the lab and in the cloud forests of Costa Rica. The footage showed that the insects always tried to keep their backs aimed toward the light, a result the team confirmed by gluing little motion trackers on the insects. In turn, the team found through computerized flight simulations that those inadvertent roll maneuvers could explain the bugs’ looping, trapped flight trajectories.
The study also offers a hint of how to mitigate the effect of lights on insects. Insects seem least affected when they fly under lights that are projected straight down, as opposed to lights that shine upward or that have been mounted horizontally. Researchers have long advised limiting light pollution by using downward-pointing light fixtures that illuminate only the nearby ground.
Image Credits
In-Article Image Credits
Why insects are attracted to light -moths swarming a light source via Wikimedia Commons by Tony Harman with usage type - Creative Commons License. June 14, 2007Featured Image Credit
Why insects are attracted to light -moths swarming a light source via Wikimedia Commons by Tony Harman with usage type - Creative Commons License. June 14, 2007
