Leaf-cutter ants are coated in rocky crystal armor, never before seen in insects - National Geographic

Along the way, the insects brave all manner of predators—and regularly engage in wars with other ants.

A new study shows that one Central American leaf-cutter ant species has natural armor that covers its exoskeleton.

In leaf-cutter ants, this coating is made of thousands of tiny, plate-like crystals that harden their exoskeleton.

Though this paper looked only at one species, Acromyrmex echinatior, Currie and colleagues suspect other related ants have the biomineral too.

Some of the nearly 50 species of leaf-cutter ants, including the ant in the study, also harbor a symbiotic bacterium to keep their gardens from becoming infected by other harmful fungi.

When Li got the results one fall morning in 2018 showing the ants are covered in a type of biomineral not previously seen in any insect, he was ecstatic.

Like all insects, ants have exoskeletons made of chitin, which is tough and flexible.

One of these experiments involved pitting these ants against a slightly larger but closely related species in “ant wars,” Li says.

Next, the researchers exposed the insects to a pathogenic fungus, which can infect ants, and is related to fungal species that cause “zombie-like” behavior.

“If you don’t know about the biomineral in this species, what does this say about the 99.9 percent of insects that have received little or no study?”