Origin of color is unclear, but evolved multiple times
Roses are red. These tarantulas are blue. They can’t see their color, so what does blue do?
Among the various tarantula hues, “the blue color is mysteriously widespread, ” says Bor-Kai Hsiung of the University of Akron in Ohio. At least one species of tarantula flashes some blue in 40 of the 53 genera he checked. Mapping them onto a tarantula family tree, Hsiung estimates that the color evolved independently at least eight times. At first, he wondered if color among the colorblind spiders was a by-product of some more useful trait. But evidence led elsewhere.
Tarantula blue comes solely from hair. Underneath even the most eye-popping sapphire locks, spider cuticle is a dull dark. Like 90 percent of the blue coloration in nature, Hsiung says, the tarantula hair comes to its blueness from light reflected through embedded nanoscale structures. And, oh the variety. Some species deploy an ordered phalanx of micro pancake stacks, each with cuticle layers