Leaf-Cutter Ants Have Rocky Crystal Armor, Never Before Seen in Insects

Leaf-cutter ants are named for their Herculean feats: they chomp foliage and carry unwieldy pieces, like green flags many times their size, long distances to their colonies. There they chew up the leaves to feed underground fungus farms. Along the way, the insects brave all manner of predators — and regularly engage in wars with other ants. But these insects are even tougher than previously thought. From a report: A new study shows that one Central American leaf-cutter ant species has natural armor that covers its exoskeleton. This shield-like coating is made of calcite with high levels of magnesium, a type found only in one other biological structure: sea urchin teeth, which can grind limestone. Bones and teeth of many animals contain calciferous minerals, and crustaceans, such as crabs and lobsters, have mineralized shells and other body parts. But before this finding, no type of calcite had been found in any adult insect.

In leaf-cutter ants, this coating is made of thousands of tiny, plate-like crystals that harden their exoskeleton. This “armor” helps prevent the insects from losing limbs in battles with other ants and staves off fungal infections, according to a paper published November 24 in the journal Nature Communications. The discovery is especially surprising because the ants are well known. “There are thousands of papers on leaf-cutter ants,” says study co-author Cameron Currie, an evolutionary biologist at the University of Wisconsin-Madison. “We were really excited to find [this in] one of the most well-studied insects in nature,” he says. Though this paper looked only at one species, Acromyrmex echinatior, Currie and colleagues suspect other related ants have the biomineral too.