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More on the Monarch

by Patrick
Publish date
20 March 2013
Comments (3)

The Wanderer Butterfly, or Monarch, is probably the most recognisable butterfly in the world. It populates children's books and is the classical species used to illustrate insect life cycles. The Children's Museum at Melbourne Museum has housed enormous replicas of the Wanderer caterpillar, pupa and adult for the last 13 years.

Butterfly models in museum The giant butterfly, pupa and caterpillar in the Children's Gallery at Melbourne Museum.
Image: Patrick Honan
Source: Museum Victoria

Wanderer caterpillars feed on plants known as milkweeds. In Australia these include plants introduced from Africa and South America, such as Asclepias and Gomphocarpus. One of the most common is the Swan Plant (Gomphocarpus fruticosa), which may have been accidentally introduced as part of the regular trade between Australia and South Africa, or deliberately introduced for the 'silk cotton' to assist in hat making. This species is considered a noxious weed in some parts of Australia, and its abundance has been dramatically reduced by weed control programs, leading to a concurrent reduction in Wanderer populations around Melbourne.

Caterpillars feeding Caterpillars feeding on the Swan Palnt, Gomphocarpus fruticosa.
Source: Patrick Honan

Milkweeds contain poisons called cardiac glycosides which are absorbed by the caterpillars and used for their own defences. These poisons affect the hearts of vertebrates such as birds, inducing vomiting at half the lethal dose. Wanderers advertise the fact that they are poisonous to eat with contrasting patterns of yellow and black in the caterpillar, and orange and black in the adult. The chemicals are concentrated in the tips of the wings of adults, so any bird venturing a taste will cop a full dose and leave the butterfly alone.

Wing of butterfly. The warning colours on the hindwing of a Wanderer Butterfly. The black spot is the 'sex gland' of a male.
Source: Patrick Honan

The caterpillars themselves also become victims of their own food plants. Studies in the USA show that up to 30 per cent of very young caterpillars become glued to the leaves of milkweeds by latex in the sticky sap. And when its first bite ingests an unusually high quantity of cardiac glycosides, a newly-hatched caterpillar may become seized for ten minutes or more in a state of catalepsis before recovering.

Caterpillar feeding A late-instar caterpillar addressing the milky sap of Asclepias rotundifolia.
Source: Patrick Honan

Despite this, some birds such as Pied Currawongs (Strepera graculina) and Black-faced Cuckoo-shrikes (Coracina novaehollandiae) seem to be able to feed on Wanderers with impunity. The caterpillars are also attacked by a tachinid fly (Winthemia neowinthemoides), whose larvae feed on caterpillars from the inside, slowly killing them. In some areas, particularly coastal NSW and Queensland, these parasites account for 80-100 per cent of Wanderer larvae.

mating butterflies A male Wanderer overpowers the female (left) before flying off together and resting for several hours whilst mating (right).
Source: Patrick Honan

Mating by Wanderer Butterflies can be an aggressive experience. Males patrol patches of host plants, awaiting females. When females appear they are chased with great vigour by the males, often spiralling high into the air. Eventually the male may overpower her with the assistance of pheromones that cause her wing muscles to seize, forcing her to the ground where he mates with her. In Australia, breeding may occur year-round in the northern parts of the Wanderers' range, but in southern areas thousands of adults cluster together in trees after mating to see out the cooler months. Although not as spectacular as the roosting sites in North America that host many millions of butterflies, these clusters around Sydney and Adelaide are a memorable sight.

Female Wanderer Butterfly Female Wanderer resting during the day.
Source: Patrick Honan

Flight of the Butterflies 3D opens at IMAX Melbourne Museum on 21 March. 

Patrick's first post: Monarch or Wanderer butterfly



Orr, A. & Kitching, R., 2010, The Butterflies of Australia, Allen & Unwin, Sydney, 296pp.

Oyeyele, S.O & Zalucki, M.P., 1990, Cardiac glycosides and oviposition by Danaus plexippus on Asclepias fruticosa in south-east Queensland (Australia), with notes on the effect of plant nitrogen content, Ecological Entomology, 15:177–185.

Parsons, W.T. & Cuthbertson, E.G., 2001, Noxious Weeds of Australia, CSIRO Publishing, Melbourne, 698pp

Zalucki, M.P. & Brower, L.P., 1992, Survival of first instar larvae of Danaus plexippus (Lepidoptera: Danainae) in relation to cardiac glycoside and latex content of Asclepias humistrata (Asclepiadaceae), Chemoecology, 3(2):81-93

Wanderer or Monarch butterfly

by Patrick
Publish date
8 March 2013
Comments (13)

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 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.

Wanderer butterfly feeding 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.

Wanderer caterpillar 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.

Wanderer Butterfly pupa. 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 butterfly migration 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


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.

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