Flying insects are known to make a beeline for lights in the dark, as the saying goes, “like moths to a flame.”
Now, scientists have figured out why insects are so keen on light, but it’s not because they’re attracted to the light source.
According to a pre-print paper on the bioRxiv preprint server titled: “Why flying insects gather at artificial light,” insects don’t fly directly to lights from far away because they’re attracted to them, but they appear to change course toward a light if they happen to be passing by due to a strange innate biological response. Our results indicate that artificial light may only attract passing insects rather then directly attract them from farther away,” wrote the lead author Samuel Fabian and co-authors in their paper.
The scientists described their analysis of the flight paths of several insect species under artificial lighting to determine how insects use the dorsal light response (DLR).
“Most flying insects display some form of the dorsal-light-response (DLR), a behavior that keeps their dorsal (top) side to the brightest visual region,” the authors explained.
This DLR allows the insects to know which way is up, as the moon or sun is usually more or less directly above them, and this orientation allows them to maintain proper flight attitude and control.
The researchers found that artificial light attracts insects because of this DLR. Not only do they fly straight toward it but they also try to keep it over them.
“Contrary to the expectation of attraction, insects do not steer directly toward the light. Instead, insects turn their dorsum toward the light, generating flight bouts perpendicular to the source,” the authors wrote.
They discovered that, at close range, insects fly orthogonally, not directly, to the source of light. This leads to unpredictable flight paths as their position changes relative to the light. It can cause insects to fly around lights, seemingly trapped and transfixed.
“Near artificial sources, however, this highly conserved dorsal-light-response can produce continuous steering around the light and trap an insect. Our guidance model demonstrates that this dorsal tilting is sufficient to create the seemingly erratic flight paths of insects near lights and is the most plausible model for why flying insects gather at artificial lights,” the authors said in the paper.
The fact that the insects aren’t flying directly toward the light disproves one previous theory of why insects appear to be attracted to light, which was that it was some form of escape response. Another theory suggested that the insects flew towards artificial lights because they were attracted by the heat emitted by the bulb: however, the authors disproved this too, by using LED lighting, which emits negligible infrared heat radiation, but still causes insects to flock.
” Our findings indicate that the localized light trapping of insects is caused by a disruption of an insect’s ability to control its attitude, and not navigation,” concluded the authors.
“Our experimental evidence and simulations attribute the mechanism of light entrapment to a disruption of the insect’s perception of vertical rather than a navigational cue.”
The authors suggested that a possible outcome of their research could be to help the construction industry to avoid the types of light that most attract insects.
“Taken together, reducing bright, unshielded, and upward facing lights will mitigate the impact on flying insects at night, when skylight cannot compete with artificial sources. Future research focused on spectral tuning of the visual components of the DLR would help isolate how best to alter artificial lights to avoid confusing insects flying at night.”
The paper is still a pre-print, meaning that it has not yet been peer-reviewed and published in an established journal.
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about insect biology? Let us know via [email protected]
The post Why Insects Are Drawn to the Light, According to Science appeared first on Newsweek.
