  We investigate an interacting particle model to simulate a foraging colony of
ants, where each ant is represented as an active Brownian particle. The
interactions among ants are mediated through chemotaxis, aligning their
orientations with the upward gradient of the pheromone field. Unlike
conventional models, our study introduces a parameter that enables the
reproduction of two distinctive behaviors: the well-known Keller--Segel
collapse and the formation of traveling clusters, without relying on external
constraints such as food sources or nests. We consider the associated
mean-field limit partial differential equation (PDE) of this system and
establish the analytical and numerical foundations for understanding these
particle behaviors. Remarkably, the mean-field PDE not only supports
Keller--Segel collapse and lane formation but also unveils a bistable region
where these two behaviors compete. The patterns associated with these phenomena
are elucidated by the shape of the growing eigenfunctions derived from linear
stability analysis. This study not only contributes to our understanding of
complex ant colony dynamics but also introduces a novel parameter-dependent
perspective on pattern formation in collective systems.
