Atta cephalotes soldier extends her mandibles over an Acromyrmex echinatior.

A soldier ant of the species Atta cephalotes (right) extends its mandibles towards an Acromyrmex echinatior worker ant. Mineralized body armour protects some A. echinatior workers from attack. Credit: Caitlin M. Carlson


The crystalline armour that protects ants in battle

A species of leaf-cutter ant is the first known example of an insect with mineralized armour, which shields them during combat.

Just as superheroes don armour to fight villains, so some ants make their own close-fitting protective shield to fend off attackers and parasites.

Pupa Gilbert and Cameron Currie at the University of Wisconsin–Madison and their colleagues discovered that in workers of one species of leaf-cutter ant (Acromyrmex echinatior), almost the entire body is covered in a magnesium-rich layer containing a bone-like mineral called calcite. The armour, which is made up of tiny crystals that form a curved surface, develops as the ants mature and seems to be produced by the underlying waxy outer coating of the body of mature workers.

In fights with soldiers of another ant species, worker A. echinatior ants equipped with the calcite armour lost fewer body parts and were more likely to survive than were those without the protective covering. The armour also helped to protect the insects against infection with a disease-causing microorganism.

Calcite armour is common in lobsters and other marine animals but has never before been observed in insects. The findings suggest that this type of covering might be more widespread than previously thought, the researchers say.