The largest form is the queen, which lays eggs. Unfertilised eggs produce males and fertilised eggs produce females. There are many queens in coastal brown ant nests. Males are the next largest form and are elongated in shape. By far the most numerous forms are the workers.
Workers are sterile females who care for the young, collect food, build and defend the nest.
There are two worker castes, a more numerous form with a small head and the other less numerous with a large head. The large headed form defends the colony and is sometimes known as the soldier caste. One of the ant s common names is taken from this form . Queens and males are rarely seen outside the nest. The ant is thought to have originated in southern Africa and has now spread all over the Old World tropics and into many temperate areas.