The Irken society is very hierarchical. There are several classes of Irkens which can usually be told apart by their physical appearance (see Irken Physiology). The Irken empire is ultimately ruled by the Irken control brain, which runs the Smeet hatching facility, chooses new Almighty Tallest when necessary and assigns roles to each Irken by programming their Pak.
Although Irken society seems to be highly regimented, it is possible for an Irken assigned to one class to be reassigned by the control brain to another class. There also seems to be no distinction made due to sex in assigning roles as there are several female Irken Invaders.