Monarch butterfly migration: Difference between revisions

to=== Before 1975 ===

As late as 1951, monarchs were thought to overwinter in northern latitudes as adults or pupae. Roosts of thousands were observed in southern regions of North America.<ref name=Klots>{{cite book|last1=Klots|first1=Alexander B.|title=A Field Guide to the Butterflies of North America, East of the Great Plains|date=1951|publisher=Houghton Mifflin Company|location=Boston|isbn=0395078652|pages=78, 79|edition=Tenth}}</ref>

Migrating western populations of ''D.Plexippus plexippus'' and their overwintering sites were known long before the winter sites in Mexico were located by Canadian and American researchers in the 1970s. Pre -Hispanic native Americans, the Purépecha, tied the harvest of corn to the arrival of the butterflies. Monarchs appear in legends of the people that live near overwintering areas. In the areas surrounding the overwintering sites in Mexico, local residents were quite aware of the overwintering behavior of monarch butterflies long before 1975. The local people, called the Mazahua, have lived near the overwintering sites for centuries. The arrival of the monarchs is closely tied to the traditional the Day of the Dead celebrations. Local residents today easily recall seeing the migrating butterflies prior to 1975.{{sfn|Brower|1977|p=41}}<ref>{{cite web | title = The Monarchs' Arrival in Mexico and Mexican Traditions

For at least a century, monarchs were observed overwintering in CACalifornia in the fog belt.{{sfn|Pyle|2014|p=7}} Historical records of lepidopterists do not mention the existence of monarchs in their current western range that extends northward through Washington, Oregon and Canada possibly because milkweed was not available until human disturbance expanded its range.{{sfn|Pyle|2014|p=15}}