in size and shape to the queen. The males also produce large quantities of pheromones to pacify the worker ants. Reproduction responsibilities and problems In a colony, the queen is the primary individual responsible for reproduction in the colony. Analysis of genotypes have confirmed that workers are, on average, more closely related to the offspring of the queen than to that of other workers, and that workers rarely, if ever, reproduce. Three factors have been suggested to rationalize the loss of worker reproduction in the presence of a queen. First, if the worker reproduces, it lowers the general performance of the colony because it is not working. Second, workers increase their inclusive fitness by policing other workers because they themselves are more related to the queen's offspring than other worker's offspring. Lastly, the large male larvae become too large to be transported, forcing colonies with a sexual brood to nest for a period of 41–56 days, as compared to non-reproductive colonies that remain in the nest an average of 17 days before returning to a nomadic phase. This suggests that if workers produced male offspring, they might be hatched out of sync with the queen's sexual brood and not likely to be successfully reared to adulthood. Foraging The whole colony of army ants can consume up to 500,000 prey animals each day, so can have a significant influence on the population, diversity, and behaviour of their prey. The prey selection differs with the species. Underground species prey primarily on ground-dwelling arthropods and their larvae, earthworms, and occasionally also the young of vertebrates, turtle eggs, or oily seeds. A majority of the species, the "colony robbers", specialize in the offspring of other ants and wasps. Only a few species seem to have the very broad spectrum of prey seen in the raiding species. Even these species do not eat every kind of animal. Although small vertebrates that get caught in the raid will be killed, the jaws of the American Eciton are not suited to this type of prey, in contrast to the African Dorylus. These undesired prey are simply left behind and consumed by scavengers or by the flies that accompany the ant swarm. Only a few species hunt primarily on the surface of the earth; they seek their prey mainly in leaf litter and in low vegetation. About five species hunt in higher trees, where they can attack birds