In the steep mountains of the Madeira islands are evergreen laurel forests, called laurisilva. High in their canopy is where these vivid butterflies spend much of their time. Their fiery yellow hues match those of the element sulfur, once known as brimstone—thus their common name.

But the butterflies that provide such lovely splashes of color are endangered. Madeira draws many tourists, and urban development has led to habitat loss. The life cycle of Madeira brimstones naturally limits their population growth: adults can live for several months—a long time for a butterfly—and there is likely only one new generation each year. Their caterpillars feed on just one type of tree, which is itself threatened by an invasive plant species. But there may be a bit of protection: Madeira has a vast nature preserve, and remaining laurisilva areas are now officially protected in a UNESCO World Heritage Site.