American researchers have found that a specific temperature range is critical for the proper function of butterfly wings. It was also found that these insects gracefully regulate the temperature of their wings through both structural and behavioral adaptations. Research article published in Nature Communications.
Contrary to popular belief that the wings of butterflies are composed mainly of non-living material, these organs have a network of living cells that function within a limited temperature range. Due to the low heat capacity, the wings quickly overheat in the bright sun and cool down strongly when the air temperature drops significantly.
It turned out that with the help of their wings, butterflies are able to quickly and accurately determine the intensity and direction of sunlight without using their eyes. A team of scientists figured this out thanks to a detailed study of the internal structure of the wing.
Video about the study of thermodynamics and thermoregulation of butterfly wings / © Youtube - Columbia Engineering
By carefully removing the scales from the wings and staining the neurons found inside, the scientists discovered that the butterfly's wings contain a complex network of mechanical and temperature sensors. The researchers also found a "wing heart" that beats several dozen times per minute to facilitate the directed flow of insect blood or hemolymph through androconia, a group of scales located on the wings of some species of butterflies and used to vaporize pheromones.
“Much of the research on butterfly wings has focused on the colors used in these creatures' signaling,” says Professor Naomi Pearce, one of the study's authors. "This work shows that we need to reimagine the butterfly wing as a dynamic living structure rather than a relatively inert membrane."
Also, scientists were able to study the temperature distribution on the surface of insect wings. This is made possible by a non-invasive technique based on hyperspectral infrared imaging. Previously, it was impossible to conduct such a study due to the fragility and thinness of the wing. “We found that nanostructures of various sizes and different cuticle thicknesses create a non-uniform distribution of radiation cooling, which selectively lowers the temperature of living structures such as wing veins,” says co-author Nanfang Yu.
The temperature distribution on the wings of three species of butterflies illuminated by sunlight shows that, despite the wide variation in color and pattern, the temperature of androconia and veins that contain living cells is always lower than in the rest of the organ / © Tsai, Pierce, Yu et. al, Nature Communications, 2020
To assess the influence of environmental factors (such as solar radiation, earth temperature, air humidity), scientists reproduced in the laboratory the natural habitat of butterflies. It turned out that in various species of these creatures, regardless of colors and patterns, those areas of the wings that contain living cells are always colder than the "lifeless" areas.
When butterflies were exposed to directional light that mimics the sun, the insects reacted in a specific way when they reached a certain temperature threshold (about 40 degrees Celsius) to prevent overheating. Upon reaching this temperature, the Lepidoptera turned so as to minimize heating.
This research not only reveals new features of butterfly physiology. The results of the work of American scientists can also help in the development of new heat-insulating coatings.