the world is divided into eight biogeographic areas called ecozones: palearctic, nearctic, afrotropic, neotropic, australasia, indo-malaya, oceania, and antarctica. palearctic includes most of eurasia and north africa while nearctic includes most of north america. "limenitis" butterfly wing patterns are much more diverse in the nearctic than the palearctic. three lineages of mimetic butterflies occur in north america and the evolution of mimicry may have played a large role in the diversification of this group. for butterflies to travel from the palearctic region to the nearctic region of the world, the migration must have curred during a time period when beringia, the land bridge between euorasia and north america, was still above water. based on crude divergence rate calculations, the colonization of the nearctic "leminitis" dates back approximately four million years. whether the migration event was a single or multiple occurrence event has a significant effect on how we look at the evolution of mimicry. a history of multiple migrations would suggest that speciation occurred before the evolution of mimicry, meaning mimicry was the result of speciation instead of the driver of speciation.