Climate Change May Be Fading the Iridescent Wings of Blue Butterflies

A new study suggests that climate change could be dimming the vibrant, iridescent wings of the Blue Morpho butterfly, a species renowned for its striking blue coloration. Researchers at the Smithsonian Tropical Research Institute (STRI) in Panama have experimentally confirmed that exposure to high temperatures during the butterfly's metamorphosis can weaken the wings' characteristic shimmer.

The findings, published in the journal 'Proceedings of the National Academy of Sciences Nexus,' indicate that elevated temperatures can lead to a decrease in wing brightness and a change in color. The Blue Morpho butterfly, a large species found in tropical rainforests, is famous for its intense blue wings, which are even represented in mobile phone emojis. Scientists investigated how rising global temperatures might impact these iconic insects.

To test their hypothesis, the research team exposed butterfly pupae to three different temperature conditions: a tropical environment (control group), a temperate environment, and a high-temperature greenhouse simulating a climate change scenario predicted by the Intergovernmental Panel on Climate Change (IPCC) with a 3.5-degree Celsius rise from pre-industrial levels.

The results showed that butterflies that developed in the high-temperature environment exhibited reduced wing brightness and altered colors. The researchers explained that the blue color is not due to pigment but rather to the intricate 'nanostructure' of the wing scales, which reflect light. In warmer conditions, the distance between these nanostructures decreases, causing the scales to narrow and reducing the overall reflectivity and brightness of the wings.

While the exact implications of these color changes for predator evasion or mate attraction are still under investigation, the study suggests a potential consequence. The Blue Morpho's bright, flashing wings are thought to confuse predators. If this iridescence fades or changes, the butterflies might become more vulnerable to predation. The study also noted that lower temperatures did not significantly affect the butterflies' appearance.

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The butterfly's wing scales are similar to tiles overlapping on a roof. The change in wing color in adults exposed to high temperatures is due to the distance between nanostructures decreasing, narrowing the overall width of the scales.