Pseudomyrmex nigropilosa: A Parasite of a Mutualism.

Pseudomyrmex nigropilosa is a parasite ofthe ant-acacia mutualism in Central America in that it harvests the resources of swollen-thorn acacias but does not protect the acacias. In the process, it also lowers the rate of occupation by the obligate acacia-ants, species of ants that do protect swollen-thorn acacias. Tenancy ofan acacia by P. nigropilosa must be temporary, since the unoccupied plant is shortly killed by herbivores or competing plants, or is taken over by obligate acacia-ants. As expected of a species of short-lived ant, a P. nigropilosa colony produces reproductives earlier in the life of the colony and maintains fewer grams of workers per gram of brood than does a colony of the long-lived obligate acacia-ants.