Blue Morpho, wings open

Morpho peleides

Blue Morpho · Fairchild Tropical Botanic Garden · 7 February 2026

A Blue Morpho with its wings open in the butterfly house at Fairchild, a butterfly of the rainforests of Central and South America where it glides along the streams and clearings flashing exactly this blue.

The blue isn't pigment at all. The wing scales are colourless, but stacked in layers fine enough to interfere with light the way a soap film does, reflecting blue and cancelling out everything else. That is why the colour flashes rather than sitting still: it shifts with the angle of the light and the angle you view it from, which is exactly what a pigment can't do. Blue is the rarest colour in nature for the same reason - almost nothing makes a blue pigment, so the animals that look blue have to build it.