A game theoretical model is advanced to explain the emergence time schedule of male butterflies under temporal apostatic" selection, so that males emerging on different days enjoy equal fitness in evolutionary equilibrium. The model predicts not only the position of the peak data but also the shape of the male emergence curve for any given female emergence schedule. Where the female emergence curve is smooth with one peak, a flight season can be divided into an earlier phase, when some males emerge every day, and a later phase in which no male emerges. Preemergence mortality also determines the rate coefficient of the decrease in sex ratio through the season. The model is applied to a well-studied population of the butterfly Eurphydryas editha . The male presence curve fits well, but no clear truncation exists in male emergence, and some males emerge earlier than predicted. Reasons for deviations are discussed. "