We've all noticed how much insects love to fly around lights. But why? Many answers have been proposed; some have suggested that insects have a direct attraction to the light itself; others have said the bugs want the heat; some have hypothesized that the creatures are trying to escape the dark; still another theory has been that they mistake the light for the moon, which they use for navigation. But flight patterns and other data don't fully support any of these conclusions.
New research reported in Nature Communications may have finally found an answer. The work has suggested that the insects are not so much attracted to the light as their navigational systems are totally wrecked by it. The flying bugs end up flitting around street lights and other artificial light sources because they are confusing them for a kind of beacon.
The study showed that insects have an innate sense that light comes from above. This research used careful motion capture camera techniques to image the movement of insects around artificial lights at field sites located around Monteverde, Costa Rica. This showed that insects tend to tilt their backs toward the source of light, explained study co-author Sam Fabian, an entomologist at Imperial College London.
When the only sources of light are natural, it makes sense that insects would know which way was up because of the direction of light. But when that system is totally upended because the strongest sources of light are no longer in the sky, the insects become very confused.
The research indicated that dragonflies circle continuously around light sources, with their backs positioned to face the light beam. Some insects end up flipping totally upside down when lights shine directly upward. These search-light-style systems can make insects flip and then crash land. Bright lights that point directly downward also interfered with the insects' flight behaviors.
Insects may seem like pests, but we need them for many reasons. For example, they are important pollinators that help support food production; some insect species help control the levels of other pesky insects like mosquitoes; and some research has identified insects that can reduce the spread of pathogens.
Insect populations around the world are known to be in rapid decline, and research has shown that light pollution is a major cause of those losses. The problem is severe enough to have been referred to as an insect apocalypse, and experts have encouraged the implementation of policies that could reduce light pollution or other factors like pesticides that are contributing to the decline.
Sources: Phys.org via The Conversation, Nature Communications