What ant species protects acacia trees in exchange for food and shelter?

The acacia ant protects acacia trees in exchange for food and shelter, one of nature’s best-known mutualisms. The ants defend the tree against herbivores while living in its hollow, swollen thorns.

The classic example is Pseudomyrmex ferruginea and the bullhorn acacia, Vachellia cornigera, in Central America. The tree provides shelter inside its stipular spines, sugary nectar from extrafloral nectaries, and protein-rich Beltian bodies produced near the leaf tips.

In return, worker ants patrol the plant and aggressively attack insects and browsing animals. They may also remove competing seedlings around the tree’s base. When herbivores damage a leaf, the tree releases volatile chemicals that help alert the colony, triggering a rapid defensive response.

“Acacia ant” is a common name rather than one single species worldwide. Several ant species participate in acacia partnerships, and not every relationship is equally strong. Some ants offer little protection or exploit the plant without providing much benefit. That is why the most precise species-level answer for the classic Central American example is Pseudomyrmex ferruginea.