Two-dimensional slices through the full four-dimensional initial-condition space. Parameter values are fixed as per Figure3. Period-3 attractors are labelled in blue, period-5 attractors in green and chaotic attractors in red. White is empty space where there was no sample taken. The initial-condition space is restricted to the lower triangular region due to the condition S(0) + I(0) + R(0) + W(0) = 1. 5000 randomly selected data points are presented from the complete 250,000 simulations performed for clarity of presentation. The relative proportions of each type of attractor determined from the full data set were preserved.