The various species of wasps fall into one of two main categories: solitary wasps and social wasps. Adult solitary wasps live and operate alone. Most do not construct nests. All adult solitary wasps are fertile. By contrast, social wasps exist in colonies numbering up to several thousand strong and build nests. However in some cases not all of the colonies wasps can reproduce. In the more advanced species, just the wasp queen and male wasps can mate, whilst the majority of the colony is made up of sterile female workers.