Schematic describing all five models. Quantities represented in the Ross, Macdonald, Anderson/May, McKenzie and Chitnis models of malaria transmission. Arrows indicate directions of flow when a quantity is present in the model. R = Ross, Mac = Macdonald, A/M = Anderson/May, M = McKenzie, C = Chitnis. *Susceptible mosquitoes are not included directly in any model, but Chitnis includes the total mosquito population, so susceptible mosquitoes are implicitly modeled.