Safari Ltd Life Cycle of a Stag BeetleSafari Ltd Life Cycle of a Stag Beetle Whereas the life cycles of many insects are measured in weeks, the stag beetle takes years to develop. Eggs are laid in rotting wood, where larvae grow for six years before becoming pupae. Development speeds at that point, and in a few weeks, the adult stag beetle emerges. Characteristics: The most striking characteristic of the adult stag beetle is its massive mandibles. The insect received its name because they