A chemical messenger that influences the behavior of other individuals is a(n) .

The chemical messenger that influences the behavior of other individuals is known as a "pheromone."

Pheromones are substances produced and released into the environment by an animal or plant, affecting the behavior or physiology of others of its species. They can serve various functions, such as indicating territory, signaling danger, attracting mates, or coordinating group behaviors. For example, in ants, pheromones play a crucial role in communication and foraging activities. The detection of pheromones usually occurs through olfactory receptors, and the response can lead to significant changes in behavior or social dynamics within the species.

In summary, pheromones are essential in the realm of animal behavior and ecology, influencing interactions among individuals in a variety of species.