Taking In the Welcome Mat

Abstract

ECOLOGY/EVOLUTION Ants are ubiquitous in tropical forests, and they exhibit a wide variety of nesting and foraging behaviors that have fascinated naturalists and ecologists ever since the pioneering of scientific exploration in the tropics. Despite many decades of intense study and the high visibility of ants, Longino has managed to unearth previously unreported nesting habits in two endemic Costa Rican ant species in the genus Stenamma . These ants build nests in the vertical clay banks of streams, and the entrance to the nest is formed by a tunnel through the center of a shallow dish sitting atop a pedestal of clay or through a similarly shaped disk of soil lying on a mound of small stones. In both types of dwelling, a spherical pebble near the entrance can be retrieved and used to plug the doorway in times of danger. Each ant colony maintains several such nests, but occupies only one at a time. Because of their colonial habit, ants attract predators, and much of their nesting repertoire revolves around defense. Hence, it appears that the elaborate constructions of Stenamma may minimize the chances of attack by marauding hordes of army ants, which are one of the dominant forces shaping tropical forest ecosystems. — AMS Biotropica 37 , 670 (2005).