Moth wings are beautiful in infrared light

The drab gray and brown coats of moths may not capture our imaginations as much as their colorful butterfly cousins, but according to a recent study, that’s more a fault of human vision than the moths themselves.

By photographing the wing scales of 82 moths from 26 different species using a camera that captures an extremely broad spectrum of light, the researchers observed the insects in the infrared spectrum: wavelengths of light too long for humans to see. In the infrared, the bright red and beige wings we’re used to seeing fluttering around outside lights take on vivid, iridescent colors, the researchers reported in Journal of the Royal Society Interface.

In addition to revealing the moths’ beauty, the new data also reveal species-specific structural differences in the way the insects’ wings reflect and scatter infrared light. The variety of these infrared features — which come from microscopic scales that cover moths’ wings — could eventually help scientists identify moth species using lidar (light detection and ranging), an instrument that emits and senses infrared light .

Scientists already use radar to count moths in the field. But details about the species can help scientists track the various nocturnal migrations of the creatures, which serve as major food sources for birds and other animals.

Radar entomologist Alistair Drake of the University of New South Wales in Australia notes the potential limitations of lidar for monitoring moths. “The thing about lidar is that it has a very narrow beam,” says Drake, who was not involved in this study. Radar beams used to detect insects can be 60 to 100 feet in diameter, large enough to pick up many individual organisms flying past, while lidar beams span only a few inches—about the size of a hawkmoth. “So we really don’t know if a vertically aimed lidar beam will produce enough insect crossing to be useful.”

To test the proposed moth-spotting method, lead study author Meng Li, an optics expert researching instruments for remote insect detection at Lund University in Sweden, and her team evaluated how well the lidar picked up different moths around their study site. “We’ve been monitoring since April with radar, lidar and trap,” she says. “So if there’s a big migration of certain moths, it’s going to show up in all three.”