Life history describes the birth, growth, reproduction and death of an organism. Life history theory attempts to explain how such features have evolved and influence various aspects of a species' biology, e.g., morphology, behavior, ecological interactions and population dynamics. In ants, life history details are complicated by sociality. Biologists are interested in understanding the life histories in order to better understand individual species, ants as a whole and, more generally, the evolution of sociality.
The Antwiki webpage The Ant Life Cycle provides a general introduction to the life cycle of an ant colony.