This is the reason why most flying insects are attracted by a close light source.

They say like a moth to a flame describes a deep sense of attraction. Moths are really attracted to lights. Why are they so much attracted to lights? Or why are they attracted to it that they fly straight into it? According to entomologists, scientists who study insects, they aren’t sure. However, moths (and many other flying insects) are probably more disoriented by a close light source than they are attracted to it.

Related media: Why Moths Are Obsessed With Lamps

Like A Moth To A Flame

Its believed that moths aren’t so much attracted to the glow of a flame or other bright light as they are disoriented by it. For many flying insects, they tend to find their way with the brightness of a light source as a compass. In the case of that light source being the sun or moon (natural source), the source seems very far away, so incoming rays hit the insect parallel to each other. For this reason, evolution has made moths and other flying insects to adapt by receiving that source of light with one part of their eye, a phenomenon known as transverse orientation.

Here’s the catch: moths tend to fly as much as possible in a straight line, and this visual pattern seems not to change. But if that light source is say a bulb nearby (artificial source), for instance, the angle at which the incoming light strikes the moth’s eye quickly change while it tries to hold on to that linear course. Moths have evolved to maintain a constant angle to the light that’s from a natural source, but in the case of an artificial source, it does so in a spiral towards the light and might end up attached to the source.

Image: Kay Enn’s Cafe / iStock / Getty Images Plus

The Bugging Theories

Light sources that emit ultraviolet lights as well as visible light are more likely to attract moths. We can’t see ultraviolet, but insects depend on it because many flowers have patches of ultraviolet colors on them to help their pollinators locate them. Moths might mistaken the artificial sources with ultraviolet light as bug zappers for a lush meadow of flowers and fly straight into their doom. Another theory says that infrared light sources might look like infrared reflection from their pheromones — chemical signals that attract mates. A moth might be lure by some light source as a sexy dangling mate and fly into doom. How tragic!

In a 2016 study by a team of biologists published in the peer-reviewed Journal of the Royal Society of Biology Letters, they analyzed the evolutionary consequences of how our modern, artificially-lit world would have on moths. For their study, they tested how the flight-to-light behavior of 1,048 adult ermine moths (whose larvae was collected in 2007, right after the moths’ first molt) would be affected by artificial light sources. Out of the total number of moths, 320 were rural moths who lived under dark skies, whereas the other 728 were urban moths from densely light-polluted cities. 

Rural Moths Vs Urban Moths

Ermine moth (Yponomeuta cagnagella). In 2016, two scientists in Europe tested the flight-to-light behavior of 1,048 of these moths, to find out how artificial lights might be causing them to evolve.

The moths were then raised in a lab with 16 hours of daylight and 8 hours of darkness each day. They were then released in a flight cage with a fluorescent tube at one side after two to three days of being fully developed moths. With the moths from urban areas (light-polluted) being less significantly attracted to the light than those from rural areas. The moths from urban areas with light pollution had a 30 percent reduction in the flight-to-light behavior — an indication that their species were evolving as predicted by the biologists — by staying away from artificial lights. 

This change is increasing the reproduction rate of these urban moths; but that’s making them less likely to fly around. By avoiding lights, they fly less to pollinate as many flowers or feeding as many bats. Whose starving by now? And so, even among moths, we have another example of how humans are affecting nature! Here’s the bottom line: There might be several theories as to why moths — and other flying insects — are attracted to lights.

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Written by: Nana Kwadwo, Sat, Jan 30, 2021.


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