The Wanderer Butterfly is known overseas as the Monarch Butterfly, so named for being the King, or Queen, of butterflies. In North America they are also known as King Billies, after William of Orange. The Australian name of Wanderer comes from its remarkable habit of long distance migration. The scientific name Danaus plexippus was bestowed by Carolus Linnaeus, the father of taxonomy and inventor of the scientific naming system.
Adult female Wanderer Butterfly
Source: Patrick Honan
Although not a native to Australia, the Wanderer may not exactly be introduced in the usual sense. Wanderer Butterflies most likely arrived in Australia across the Coral Sea from Vanuatu or New Caledonia, carried by three cyclones in early 1870. This was part of a major expansion in distribution across the Pacific and Atlantic Oceans from North America in the late 1800s, probably due to a combination of environmental factors, human movement and natural expansion.
An adult Wanderer Butterfly feeding on Cat's Whiskers (Orthopsiphon aristatus).
Source: Patrick Honan
The first recorded observations from Australia were made in February 1871 in Queensland, followed by the first record from Melbourne in April 1872. It is possible that Wanderers had been making the journey to Australia since time immemorial, but only after Europeans established their food plants here could Wanderers establish.
The distinctive fleshy 'filaments' behind the head of the caterpillar are used as sensory organs.
Source: Patrick Honan
Wanderers have been seen at sea up to 500km from land and occasionally settle on passing ships. This is not unusual – with favourable winds, Australian butterflies such as Common Eggflies often end up in New Zealand. Wanderers have a cruising speed of about 30km per hour with bursts of up to 50km per hour when alarmed.
The wings of the adult can be seen through the walls of a Wanderer Butterfly pupa.
Source: Patrick Honan
In North America, Wanderers undertake a famous annual migration from Canada and northern USA down to Mexico and California, and then back again. The populations overwintering in the Oyamel Fir Forests of Mexico roost at densities of 10 million butterflies per hectare. Because the length of time required for the migration exceeds that of an adult Wanderer's life span, those arriving back in Canada are the descendents of those that left the year before.
Map of the North American migration of the Monarch or Wanderer butterfly that occurs each year in autumn.
Source: Via the Frost Lab, Queen's University
Department of Psychology
The secrets of the Wanderer migration in North America weren't fully revealed until the 1970s. Canadian Dr Fred Urquhart was fascinated as a child by the question of where all the Wanderers disappeared to during winter, and he and his team of volunteers took nearly 40 years to discover the answer. Professor Urquhart died in 2002 but his life-long search is the subject of the new film Flight of the Butterflies 3D. In Australia, Dr Courtenay Smithers from the Australian Museum began tagging Wanderer Butterflies in the 1970s using many volunteers from the broader community. His studies revealed that overwintering populations around Sydney and Adelaide move into Melbourne and surrounds during summer. This research continues, with many questions still to be answered. In certain years, for example, populations appear to overwinter in some parts of Victoria, such as Phillip Island and the Western Districts, without needing to move interstate, but more data is needed to confirm these observations.
Flight of the Butterflies 3D opens at IMAX Melbourne Museum on 21 March.
Patrick's next post on these butterflies: More on the Monarch
References:
Clake, A.R. & Zalucki, M.P., 2004. Monarchs in Australia: On the Winds of A Storm? Biological Invasions, 6:123-127
McCubbin, C., 1970, Australian Butterflies, Thomas Nelson Ltd, Melbourne, 206pp.