Figure 3.

Median number of sperm used per egg for all 25 queens, plotted as a function of queen age. Where queens have been measured at more than one age, the data points (open circles) are connected by a line. The dotted lines represent the calculated maximum sperm use per egg that queens can afford in order to produce colonies that reach sexual maturity (inferred to be at 5 years of age), with the different lines representing different initial sperm numbers after mating (see inset). The light grey background circles show sperm use of surviving queens as simulated by the heuristic model and illustrate that colony survival is expected to decline rapidly after colonies have reached sexual maturity at 5 years of age, and only queens that store a high number of sperm and use their supply prudently will be able to produce sexual offspring during multiple seasons.