  Collective escaping is a ubiquitous phenomenon in animal groups. Symmetry
breaking caused by panic escape exhibits a shared feature across species that
one exit is used more than the other when agents escaping from a closed space
with two symmetrically located exists. Intuitively, one exit will be used more
by more individuals close to it, namely there is an asymmetric distribution
initially. We used ant groups to investigate how initial distribution of
colonies would influence symmetry breaking in collective escaping.
Surprisingly, there was no positive correlation between symmetry breaking and
the asymmetrically initial distribution, which was quite counter-intuitive. In
the experiments, a flee stage was observed and accordingly a flee-pheromone
model was introduced to depict this special behavior in the early stage of
escaping. Simulation results fitted well with the experiment. Furthermore, the
flee stage duration was calibrated quantitatively and the model reproduced the
observation demonstrated by our previous work. This paper explicitly
distinguished two stages in ant panic escaping for the first time, thus
enhancing the understanding in escaping behavior of ant colonies.
