Exotic Invasives in Asia

Paul Cherubini paulcher at concentric.net
Wed Sep 16 17:14:30 EDT 1998

The "swan plant" referred to in this post in Asclepias fruiticosa. It is
an African milkweed that became established in Australia and New Zealand
in the mid-1800's.  The monarch butterfly became established there and
on other Pacific island in the late 1800's, coinciding with the advent
of fast moving steam powered ships.

One theory is that the monarch became introduced to Hawaii/Australia/New
Zealand inadvertently when caterpillars wandered off milkweeds growing
in shipyards and pupated on merchandise that was loaded on the steam
powered ships.  Butterflies which emerged before the ship arrived in a
port could have simply stayed aboard ship for several days.

Another possibility is that monarchs in high altitude migration and
blown out to sea by strong winds decended on ships they encountered and
stayed with the ships until they arrived at a port.  Monarchs are well
known to cluster at night on offshore oil drilling rigs in the Gulf
coast during the fall migration in mid-October.

Paul Cherubini, El Dorado, California
paulcher at concentric.net

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