“These two species of peacock spiders raise and wiggle their abdomens toward potential mates during courtship to display every color across the entire visible spectrum” – a complete rainbow of color – “making this the first true rainbow-iridescent signal known in animals.”
A range of techniques were employed to find out how they do this, including using electron microscopy, which uses incredibly precise beams of electrons to uncover the finest details of a sample. When they began to spot a few telltale structures, they opted to use 3D printing to produce nano-scale prototypes in order to test out their ideas.
It turns out that these spiders are armed with novel scales that coat their abdomens. As well as being curved in highly specific ways, the scales also appear to be adorned with a grate-like pattern, one that diffracts (bends) waves of light.
Combined, both features allow these critters to manufacture a full spectrum of color. Considering how spectacular the visual senses of the peacock spiders are, the team suspect that this ability likely evolved as “a direct product of sexual selection through female choice.”
As cool as this discovery is in isolation, the team highlights how this could help engineers develop remarkable new materials. This ability to produce a rainbow of color on such a small scale and to such a remarkable degree of precision could lead to plenty of bio-inspired designs – anything from fancy advertisements to highly portable spectrometers.
These little legends truly are the gift that keeps on giving.