A mating system in which a female mates with more than one male. In animals it is relatively rare compared to monogamous or polygynous systems, but occurs across a wide spectrum of animal groups, including certain human societies. In simultaneous polyandry, sperm from multiple males compete to fertilize eggs. For example, a honey bee queen will mate with several males during her courtship flight, and store their sperm throughout her life. In sequential (serial) polyandry, a female mates with a single male, leaving him for another male when her eggs have been fertilized and laid. The usual sexual dimorphism is often reversed in polyandrous females, which tend to be larger than their male counterparts. In flowering plants, polyandry is the norm, with pollen from multiple donor plants being deposited on the same stigma, leading to fruits with different paternity. Exceptions are plants that perform self-fertilization or that receive pollen in discrete packages from a single donor. Compare polygyny.