Leaf-cutting ants are significant pests throughout the Neotropics. Among them, the grass-cutters are considered pests of pastures and sugarcane fields. Hexanic and alcoholic extracts of the plant Ageratum conyzoides were tested topically on workers of the grass-cutting ant Atta bisphaerica. They had some insecticidal effect but the respiratory rate of these ants was affected only by the alcoholic extract.