Orientation of the army ant neivamyrmex nigrescens: Integration of chemical and tactile information

Abstract

The success of the large-scale raids and emigrations of the army ant Neivamyrmex nigrescens (Cresson) depends upon their ability to orientate by responding to a chemical trail and to tactile stimuli provided by physical objects. Laboratory experiments showed that the workers' response to tactile stimuli increases in the absence of a chemical trail. Under these conditions, test ants behave much as they do in the field at a raiding front. This may explain why raiding columns are typically established along the base of rocks, fallen tree trunks, and other inanimate objects. Other experiments show that tactile stimuli may, in turn, facilitate the ants' orientation to weak chemical trails.