The Monarch Butterfly, also known as the Wanderer Butterfly in Australia, is quite prevalent in urban areas of the states of Queensland, New South Wales, Victoria (rare) and South Australia today.
There are, however, no reports of Monarch butterfly in Australia before 1871.
So how did it get here?
The Milk Weed (Asclepias curassavica) is native to North America. Its fluffy seed pods were commonly used by people as fillings for their pillows. It is believed that during theAustralian Gold Rush in the 1850s American miners brought with them their milk weed seed stuffed pillows. When these pillows were eventually discarded the seeds germinated the milk weed plant took root in Australia. Over time these plants thrived in their new Australian environment.
Monarch Butterflies, are also native to North America. One of the favourite foods of the monarch butterfly caterpillar is the milk weed. The sap of the milk weed plant contains poisonous glycosides. The butterfly's caterpillar is immune to these toxins and happily munches through the leaves of this plant and the glycosides it consumes makes the caterpillar and the adult butterfly poisonous to its predators.
So we need the milk weed plant if we expect to find mornarch butterflies.
An examination of the world-wide distribution of the butterfly today shows an unmistakable trail from the Pacific Coast of America, through Hawaii and the Pacific Islands, to Australia (see Map).
There are no reports of this butterfly in Australia before 1871. The most credible theory is that is that they appeared in Australia after the arrival of the Milk Weed plant. So how did it get here?