These “Ants” Use Ultrablack to Warn Predators — and Stay Cool

Nature has mastered the art of darkness. From the birds-of-paradise with their specialized feather structures that create a deep, matte black to the wings of certain butterflies with nanostructures that minimize light reflection, nature’s examples of deep black are impressive. But one of the striking examples comes from the ground-dwelling velvet ant.

This ant, which is actually a flightless wasp, sports a exoskeleton that mixes ultrablack regions with white areas. Researchers studying the cuticle of Traumatomutilla bifurca, a species of velvet ant, have uncovered how microscopic structures in its exoskeleton absorb almost all visible light, creating this intense darkness.

Goth ants flightless wasps

When an object reflects less than 0.5% of incoming light, scientists refer to it as “ultrablack.” In contrast, typical black clothing reflects 3-5% of light. Achieving this ultrablack effect involves more than just pigments; it requires intricate microstructures.

Vinicius Lopez, an entomologist at the Federal University of Triângulo Mineiro in Brazil, led a team using advanced imaging techniques like scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They discovered that the velvet ant’s cuticle is covered in dense nanostructures — grooves, hollow interiors, and layered lamellae — that scatter light repeatedly until it is almost entirely absorbed.

OK, but why?

In nature, ultrablack colors serve a purpose. For peacock spiders and birds-of-paradise, ultrablack enhances the contrast of bright mating signals. For velvet ants, however, ultrablack likely acts as a warning to predators. Known as aposematism, this strategy uses contrasting colors to signal danger. Velvet ants, equipped with powerful stings and tough exoskeletons, amplify their warning message with this intense blackness.

Interestingly, only female velvet ants exhibit this ultrablack coloration. The winged males are less dark, possibly because they rely on flight to avoid predators.

One might expect that such dark colors would lead to overheating under the sun, but the study found otherwise. Using thermal imaging, researchers discovered that T. bifurca remained slightly cooler than the surrounding environment. This suggests that the insulating properties of the dense setae might play a more significant role in temperature regulation than color alone.

No wings? Just get blacker — and tougher

It’s not clear why, but male and female velvet ants differ in their blackness. This could also be linked to predation.

Female velvet ants are typically flightless and rely more heavily on aposematic (warning) coloration, including ultrablack regions that enhance the visibility of their bright warning colors. Males, on the other hand, are winged and generally do not display the same level of ultrablack coloration, possibly since they are less exposed to predation risks and rely more on mobility for survival.

This coloration isn’t their only line of defense. Previous research shows that velvet ants possess a robust exoskeleton that is remarkably tough to pierce. Combined with their powerful sting, chemical alarms, and audible warning stridulations, velvet ants are well defended from attacks by birds, lizards, mammals, and amphibians​. These adaptations have likely evolved due to the flightless nature of females, who spend significant time exposed while searching for host nests.

Can we use this for ultrablack materials?

Humans have also gotten pretty good at designing ultrablack materials. Vantablack, one of the most famous such materials, absorbs 99.996% of any incoming light. However, engineers and designers are increasingly turning to nature for inspiration, a field known as biomimicry. By studying the nanostructural adaptations of creatures like velvet ants and birds-of-paradise, researchers can design more efficient and robust ultrablack surfaces for applications in optics, solar energy, and stealth technology.

The ultrablack microstructures found in velvet ants could inspire innovations in:

1. Optical Devices: Surfaces that minimize light reflection are crucial for telescopes, cameras, and sensors. Applying nature-inspired microstructures could improve these devices’ efficiency and accuracy.
2. Camouflage Materials: Military and defense industries could benefit from coatings that reduce light reflection, making objects harder to detect.
3. Solar Energy: Improving the light absorption of solar panels is a constant goal. Microstructures that mimic those found in T. bifurca might increase the panels’ efficiency, capturing more sunlight and converting it to energy more effectively.
4. Aesthetic Design: From fashion to automotive industries, ultrablack coatings offer new possibilities for creating stunning, high-contrast designs.

The study was published in the Beilstein Journal of Nanotechnology.