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Several thousand specimens of arctic butterflies were accumulated in the Canadian Northern Insect Survey. When the distributions of the various species were recorded and plotted on a map, some evidence appeared that these insects entered Canada in postglacial times from the northwest, and from the south. There is also some evidence that a few may have come from the north. The most common invasion was from the northwest, and it appears that some, such as Erebia youngi Holl., probably entered Canada rather recently, as it is only known to occur in the Yukon. Boloria pales D. & S. occurs from the Yukon to within about 150 miles west of Hudson's Bay. Colias boothii Curt. occurs as far east as Southampton Island, and Erebia rossii Curt. is distributed to Baffin Island. Others such as Boloria polaris Bdv. have spread to northern Quebec and Labrador. Thus it appears that there are successive stages of distributional spread from the northwest.