  We consider a class of stochastic processes modeling binary interactions in
an N-particle system. Examples of such systems can be found in the modeling of
biological swarms. They lead to the definition of a class of master equations
that we call pair interaction driven master equations. We prove a propagation
of chaos result for this class of master equations which generalizes Mark Kac's
well know result for the Kac model in kinetic theory. We use this result to
study kinetic limits for two biological swarm models. We show that propagation
of chaos may be lost at large times and we exhibit an example where the
invariant density is not chaotic.
