The animal world goes in hard for impressive colors, from those that blend in perfectly with their surroundings to those born to stand out and seem dressed to impress. However, new research has revealed an insect species with markings so black, they’re classed as ultrablack, absorbing nearly all visible light.
The species in question is Traumatomutilla bifurca, a type of velvet ant – which is, somewhat confusingly, actually a species of wasp. Some of these wasps don’t have any wings, but they do have fluffy little bodies, which is where their name comes from. T. bifurca in particular is famous for its distinct black and white markings and is found widespread across Brazil.
While studying color production in insects, a team of researchers discovered that this particular velvet ant species’ cuticle, a layer of its exoskeleton, had a surprising structure; under all that fluff was an arrangement of stacked platelets, like the middle of an accordion.
This stacking within the cuticle might be the key to producing the matte ultrablack color. Ultrablack is a rare pigment that reflects less than 0.5 percent of the light that hits its surface, and is of interest to those producing synthetic materials for use in camouflage and solar energy.
As the exoskeleton of the wasp has so many different levels, the researchers found that light is 5 percent better absorbed into the surface than it would be on a material that was flat. The team also discovered that the ultrablack cuticle of a female velvet ant not only absorbs visible light but can absorb ultraviolet light too.
Ultrablack has been seen in a few species, but is relatively rare in the animal world. Nonetheless, the team compared the cuticle of T. bifurca to other species with known ultrablack bodies and saw that it was most like those seen in peacock spiders and birds-of-paradise. The colors in the velvet ant were less reflective compared to the common birdwing butterfly (Troides helena), however.
Why these animals have evolved ultrablack has attracted some interesting theories. Some suggest it can be used in thermoregulation, to aid in predator avoidance, or even to highlight other colors in species that need to impress their mates. In the velvet ants, the coloration is thought to “ward off predators, but also may have some function in camouflage and protection against solar radiation,” write the authors.
Velvet ants are known as “indestructible insects”, in part because of their painful stings (and because they scream when threatened) but also because of their incredibly hard exoskeletons. The team implies that the structure of the cuticle that produces the ultrablack in the female wasps could also contribute to the strength of the exoskeleton and its resistance to high forces.
“In nature, you see a lot of different patterns of coloration, and we don’t really know why,” study author Dr Rhainer Guillermo-Ferreira, told the New York Times, but “every time we study velvet ants, they give us some new, interesting result.”
The study is published in the Beilstein Journal of Nanotechnology.
