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

Comments (3)

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Bonnie 24 April, 2013 17:11
Hi, Some of my students are doing work on monarch butterflies for a contest and because its becoming winter butterflies will not be out for very long and I was wondering if the museum could send 1/2 monarch butterflies to use for there work we will send them back after we have finished. Our school address is 195A Stewart St, Brunswick East VIC 3057 please email me back to know what u think. thanks :)
Discovery Centre 26 April, 2013 11:06

Hi Bonnie, thanks for the question.  Monarch butterflies are available commercially, and the Melbourne Zoo Butterfly House makes some great suggestions on how to raise and nurture monarch butterflies.  Hope this helps!

Lyn Faull 16 March, 2014 11:26
I have grown many swan plants in the Western District for the last thirty years, and have always had Wanderers visit and breed. Two years ago I sent 600 pupae to Melbourne Zoo in April. But for the last two years no breeders have come. Nor have any arrived at a nearby site which has many more food plants. Worryingly, this year there were very few other common butterflies such as Common Browns, Admirals or even Cabbage Whites. Does anyone know if this is just bad luck or an indication of trouble in butterfly populations?
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