Nests are commonly constructed underground in disused rodent nests, or similar protected positions where there is available material for insulation (2). The queen creates a circular chamber in which she builds a wax egg cell, and she lays her first batch of eggs inside. The eggs are laid on a layer of pollen, which is collected by the queen, and then covered with a layer of wax (6). After hatching, the white larvae are fed on honey and pollen by the queen. When they are fully-grown, the larvae cease to feed and develop into pupae after spinning a protective silk cocoon around themselves. During the pupal stage, the larvae undergo complex changes, and develop into adult workers. Throughout their development, the queen incubates this first brood by lying over the cell in which they grow, keeping them warm with the heat of her body (3), which in turn is produced by the metabolism of sugars derived from the nectar she collects (2). After emerging, the workers undertake the duties of foraging and nest care, and the queen remains inside the nest, producing further batches of eggs. When the colony reaches its peak, males and new queens are produced. Males develop from unfertilised eggs; after leaving the nest they fly around in search of new queens with which to mate (3). After mating, the new queens search for a place to hibernate. The colony, together with the old queen, gradually dies out in autumn, and the newly mated queens emerge from hibernation the following spring, to establish new colonies (6).