Shaded areas on the map indicate the world-wide distribution of D. plexippus
(the Monarch Butterfly). The stippled areas represent the range of the subspecies
D. plexippus plexippus, and the striped areas the range of D. plexippus
Monarchs are native to North and South America, but spread throughout much of the
world in the 1800's. They were first seen in Hawaii in the 1840's, and spread throughout
the South Pacific in the 1850's-60's. In the early 1870's, the first monarchs were
reported in Australia and New Zealand.
You may be wondering how monarchs traveled across the Pacific Ocean. You are not
alone. Researchers are still unsure exactly how and why the monarch made its journey
across the ocean. A few hypotheses have been formulated. It is possible that they
were transported by the numerous ships that made the long voyage across the Pacific
Ocean. Because larvae have to move around a lot to find suitable pupation sites,
and since milkweed can be found around shipyards, it is possible that the larvae
were transferred onto ships where they could travel a long distance before emerging.
It is also possible that overwintering adult monarchs landed on ships and then were
carried across during the winter. Even these hypotheses seem a little far-fetched,
however. It is most likely that humans were involved in the process, but it is not
known to what extent. Monarchs in North America can fly over 2,200 km during their
migration, so it is possible that some made the journey on their own!
Ackery, P.R., and R.I. Vane-Wright. 1984. Milkweed Butterflies: Their Cladisitics
and Biology. Ithaca, NY: Cornell University Press.
Gibbs, George. 1994. The Monarch Butterfly. Auckland, New Zealand: Reed
R.I. Vane-Wright. 1993. The Columbus Hypothesis: An Explanation for the Dramatic
19th Century Range Expansion of the Monarch Butterfly. pp. 179-186 in Biology
and Conservation of the Monarch Butterfly. Los Angeles: Natural History Museum of
Los Angeles County.