They've gone out to do different tasks, and the rate at which they meet as they come in and out of the nest entrance determines, or influences, each ant's decision about whether to go out, and which task to perform.
Saíram para realizar diversas tarefas, e o ritmo a que se encontram, quando entram e saem do ninho determina ou influencia a decisão de cada formiga sobre onde ir e que tarefa realizar.