Far North Do Monarchs Migrate?
In the Province of Ontario, as mining and logging roads were built and as towns and villages followed, the range of milkweed (A. syriaca) expanded northward, followed by a range expansion by the monarch. At present, the northern range of the monarch butterfly in Ontario appears to be a line from east to west across the province which follows our most northern major highway--The Trans Canada Highway (both northern and southern routes, #17 and #11) through Kirkland Lake, Kapuskasing, Hearst, Geraldton, Dryden, and Kenore.
The area north of the Trans Canada Highway is sparsely
inhabited and consists of dense, rugged forest and terrain. However, monarchs
have strayed as far north as James Bay!
The most recent international range expansion of the monarch butterfly that I know of is a colony that has established itself in southern Spain! Monarch butterflies are not native to Great Britain and Ireland, but individuals are found in the south each year. These may have been blown there by strong winds from the Azores, Maderia or the Canary Islands. In Great Britain, I believe the monarch is also called the "Wanderer."