Interestingly, this intraspecific variation in sex pheromone has evolved even though the two populations are only 50 km apart. In oblique banded leafrollers Choristoneura rosaceana (Walker) there is no difference in the response of males to female sex pheromone between populations found in Eastern and Western North America, which are separated by thousands of kilometres . This might indicate that distance between populations is less important than selection pressure within a geographical area.