Blue Morpho butterflies have captivated the human eye for centuries: we even have one as an emoji on our phones! In a recent experiment, researchers at the Smithsonian Tropical Research Institute (STRI) documented for the first time that hot temperatures during their development can reduce the brightness of their iridescence. In hot temperatures, such as those projected in warming future scenarios, the structures responsible for their iridescent color could change enough that common bird predators and other butterflies from the same species would likely see a color change. Scientists gathered their results in a recent publication in the journal Proceedings of the National Academy of Sciences Nexus.
Scientists exposed Morpho helenor pupae, the stage of metamorphosis before adulthood, to three different temperature categories: average tropical temperature, in which these butterflies normally live, temperate temperature, simulating temperatures in temperate zones, and hot temperatures, such as those predicted by climate change.
Consistent with other studies, they found that temperate and hot temperatures extend the time they spend as pupae. Moreover, in hot temperatures pupae died more often. They also found that adult Morpho butterflies from hot temperatures were duller, and that common bird predators and butterflies from the same species could detect a color change. The effects of this color change on predators or possible partners is still unknown. As iridescence might confuse predators, duller or color-altered butterflies might be more susceptible to predation or less attractive for possible mates.
"Here we show that iridescent animals are susceptible to the environmental conditions in which they develop. Under a warming climate, the color of some of our favorite iridescent animals can be altered and the brightness of their iridescent display dulls," explained lead author of the study and STRI fellow Juliette Rubin.
The blue iridescent color we see in Morpho butterflies doesn't come from pigments. It comes from very tiny, ridged structures on the scales of their wings called nanostructures. The blue color we see is a product of how the light is reflected by these microscopic pieces. "The scales on these butterflies are like tiles overlapping on a roof. The change in color we found in adults after exposing pupae to hot temperatures can be partly explained by the distance between nanostructures shrinking, narrowing the entire scale," explained Rubin. "This probably caused less overlapping between the scales."
The results of this study might help make predictions about the effects of raising temperatures in the development of different animals. Overall, the flexibility of these tiny structures is surprising, revealing how even the smallest natural designs can respond to a changing climate.
"This study would not have been possible without STRI's facilities and laboratories located within the natural, tropical distribution of these dazzling butterflies, offering a unique opportunity to perform our experiments. STRI also provided the chance to work with fellows and interns from multiple countries, creating a collaborative team of curious scientists," added Rubin.
Reference: Rubin, J. J., Camino, L. T., López-Tacoaman, Y. F., Wagh, P. R., Hernández Campos, G. C., & McMillan, W. O. 2026. Hot temperature during development alters iridescence in Morpho butterflies. PNAS Nexus, 5(8), pgag243. https://doi.org/10.1093/pnasnexus/pgag243
About the Smithsonian Tropical Research Institute
Headquartered in Panama City, Panama, STRI is a unit of the Smithsonian Institution. Our mission is to understand tropical biodiversity and its importance to human welfare, to train students to conduct research in the tropics and to promote conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Watch our video , and visit our website , Facebook and Instagram for updates.
