The bright portions of the Infrared images of butterflies reveal the efforts of radiative cooling. Scientists found the portions of the wings containing living cells were consistently cooler than other parts of the wings. Photo by
Nanfang Yu and Cheng-Chia Tsai/Columbia Engineering
Jan. 28 (UPI) -- Butterfly wings aren't simply lifeless canvasses for color signalling. New research has revealed a network of living cells within butterfly wings that helps the insects maintain performance by preventing overheating and rapid cooling.
When scientists from Columbia and Harvard peeled back the scales of butterfly wings, they found a network of mechanical and temperature sensors, as well as a supportive circulatory and tracheal systems.
"Most of the research on butterfly wings has focused on colors used in signaling between individuals," Naomi E. Pierce, professor of evolutionary biology at Harvard, said in a news release. "This work shows that we should reconceptualize the butterfly wing as a dynamic, living structure rather than as a relatively inert membrane."
The delicate wings of a butterfly can quickly overheat in the sun. They can also cool down too quickly in cold environs. According to the new study, published Tuesday in the journal Nature Communications, the living cells in butterfly wings help the insects regulate their temperature.
"Butterfly wings are essentially vector light-detecting panels by which butterflies can accurately determine the intensity and direction of sunlight, and do this swiftly without using their eyes," said Nanfang Yu, associate professor of applied physics at Columbia.
In lab tests, scientists used a technology called infrared hyperspectral imaging to measure the heat distribution across butterfly wings.
"We discovered that diverse scale nanostructures and non-uniform cuticle thicknesses create a heterogeneous distribution of radiative cooling -- heat dissipation through thermal radiation -- that selectively reduces the temperature of living structures such as wing veins and scent pads," Yu said.
Though scientists studied the wings of several different butterflies, each with unique visible colors and patterns, the infrared hyperspectral imaging revealed the living portion of each butterfly wing remained cooler than the rest of the wing under a variety of environmental conditions.
"The nanostructures found in the wing scales could inspire the design of radiative-cooling materials to cope with excessive heat conditions," said lead study author Cheng-Chia Tsai, a doctoral student in Yu's group.
In behavioral tests, scientists found the butterflies regularly responded to simulated sunlight in ways that suggest the butterfly's living wings help the insect sense the direction and intensity of sunlight. Using a small light spot to precisely warm the butterflies, scientists found the insects were most sensitive to a threshold of 104 degrees Fahrenheit.
Scientists are now working to study the mechanical sensors found in living wings, with hopes of deciphering the ways different sensor networks enable unique flying patterns.