Why do the hymenoptera (ants, bees and wasps) and so many instances of complex social and eusocial species?

Most species in the genus of hymenoptera have complex social structures, because of the need to survive and reproduce more of their kind. All species in this genus build nests and have a queen which lays eggs, the adult workers are charged to take care of and raise the eggs and larvae to maturity. The workers also take meticulous care of their queen, for is she were to die, the whole nest or colony would be lost.