Even when host attractants are present, there are times when endogenous physiological mechanisms prevent female mosquitoes from responding to them and engaging in host-seeking behavior. These times include a brief postemergence period, periods of the day determined by a circadian clock, and following a blood meal before and after eggs develop, which are controlled by nervous and humoral mechanisms. Other factors such as age, nutrition, and mating status can further modulate host-seeking behavior. The interplay of these factors affects the frequency at which mosquitoes will approach a host and feed on its blood, thus affecting the rates of parasite acquisition and transmission. [References: 55]