New Zealand’s most identifiable butterfly is the monarch (Danaus plexippus). Although found in many places around the world, the monarch is considered a New Zealand native1 because it became established here on its own. Scientists believe that monarchs were blown from New Caledonia and/or Vanuatu to Australia via cyclones and then blown over to New Zealand a few years later.
New Zealand’s most recognised butterfly
The monarch is recognisable for two reasons – its main habitat2 is urban and suburban gardens and it’s our largest common butterfly. We welcome monarchs into our gardens by planting their larval3 food – milkweed species4 such as swan plants – and enjoy watching their amazing journey through metamorphosis5. Monarchs are more sensitive to cold than our endemic6 butterflies. They do not survive the harsh winters, so are less common in the far south.
| Scientific classification | |
|---|---|
| Class7: | Insecta |
| Order8 | Lepidoptera |
| Family9: | Nymphalidae |
| Subfamily: | Danainae |
| Genus10: | Danaus |
| Species: | plexippus |
The monarch’s life cycle
The monarch butterfly has one of the best-known life cycles in the insect world.
During mid-summer, the process goes from egg to adult in a month or so. The butterfly has a lifespan of 60–70 days during the summer, but this extends to 6–7 months if the butterfly pupates in autumn.
Monarchs (and all butterflies) are sensitive to air temperature11. Their growth is the strongest in warm weather12, and cooler temperatures signal a change in behaviour. Monarch butterflies in North America migrate from the colder northern regions to overwinter in California and Mexico, with some of the butterflies travelling thousands of kilometres! As the temperature warms, they return north to reproduce.
Monarch butterfly life cycle
The life cycle of the monarch butterfly. Click on one of titles to find out more about each stage.
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Adaptations to life in New Zealand
Unlike their northern relatives, monarchs in New Zealand do not appear to migrate. They have adapted13 their behaviour to suit local conditions14. When the air temperature drops to 12.8°C, monarchs look for overwintering sites. Tagging data15 shows that most butterflies stay within the area where they eclosed (became adults). Overwintering monarchs prefer sites that are sheltered from the wind, have trees with a rough bark surface on which to cling and have a nearby source of nectar16. The butterflies are mostly inactive, but on warm days, they fly, bask in the sunlight and feed. When the temperatures warm up, butterflies become active again.
Swarms form regularly to overwinter at places such as Tauranga Bay in Northland. The Monarch Butterfly New Zealand Trust Pūrerehua Aotearoa (MBNZT) was initially formed by Jacqui Knight to protect this site. Other overwintering sites include areas of Hawke’s Bay, Nelson and Christchurch. The MBNZT encouraged citizen scientists to tag butterflies to learn more about the migration and overwintering habits of monarchs. The tagging project gathered data from 2005–2021. Tagging will resume in 2025.
Threats to the monarch
Monarchs use warning colouration and toxicity17 from their larval18 swan plant food source as defence mechanisms. This is enough to keep most vertebrate19 predators away, with the exception of the shining cuckoo.
Invertebrates20 are a different story. The brown soldier bug21 (Cermatulus nasalis) uses its hollow beak as a straw to suck the insides out of larvae22. Praying mantids (Miomantis caffra Saussure and Orthodera novaezealandiae Colenso) eat them. The Tasmanian paper wasp (Polistes tasmaniensis) picks up larvae and carries them away.
The parasite23 Ophryocystis elektroscirrha or OE causes adult butterflies to have crumpled and deformed wings. Monarchs with OE are unable to fly once they emerge from their chrysalis and nothing can be done to help them. Trying to 'save' sick butterflies may actually increase the spread of OE.
Dependence on swan plants
An often-overlooked threat to monarch larvae is their dependence on swan plants. Without these plants, monarchs could not breed here. Four species of milkweed have been brought into New Zealand. The plants can reproduce naturally, but more likely, gardeners plant them to attract butterflies. The voracious larvae can quickly strip the plants, leaving hungry caterpillars to starve.
There are some other food sources available. Tweedia (Oxypetalum caeruleum) is a common garden plant with small blue flowers. Larvae will only eat the new shoots. Mature larvae (those that are in their last instar) do not need the toxins in the milkweed plants, so they can successfully pupate if they are fed alternative foods. Two suggestions include draping slivers of pumpkin or thin slices of cucumber on the milkweed stems. This will not work with small caterpillars – they won’t survive. It’s worth remembering that monarchs lay a huge number of eggs, so losing a few larvae to predators or starvation is all part of the process.
Surveys by the Moths and Butterfles of New Zealand Trust indicate that monarch numbers may be in decline24. In 2022, the monarch butterfly was declared endangered25 by the International Union for the Conservation of Nature (IUCN).
Related content
Read about how scientists gathered data about monarch butterflies in this Connected article Look out for Monarchs.
Useful links
Visit the Moths and Butterflies of New Zealand Trust (MBNZT) website.
Watch this Ted Talk by Mary Ellen Hannibal on how you can help save the monarch butterfly – and the planet.
Visit the MonarchWatch website for lots of information, including how to view how monarch larvae adapt to life in space.
In 2020 Victoria University entomologist26 Phil Lester ran a citizen science27 survey looking the prevalence of a disease28 affecting Monarch butterflies caused by the protozoan parasite Ophryocystis elektroscirrha or OE. Listen to this RNZ interview with Phil Lester looking at the study's findings.
If you are in Christchurch, check out a few of these parks for overwintering butterfly clusters.
- native: A species that lives naturally in a country, as opposed to species that have been introduced by the activity of humans.
- habitat: The natural environment in which an organism lives.
- larval: The immature or juvenile form of some animals.
- species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
- metamorphosis: A profound change in form from one stage to the next in the life history of an organism.
- endemic: Native to only one location. For example, species endemic to New Zealand naturally occur only in New Zealand but may have been introduced elsewhere in the world.
- class: A classification grouping that ranks above order and below phylum (kingdom > phylum > class > order > family > genus > species).
- order: A classification grouping that ranks above family and below class (kingdom > phylum > class > order > family > genus > species).
- family: A classification grouping that ranks above genus and below order (kingdom > phylum > class > order > family > genus > species).
- genus: (Plural genera) A division used in the Linnean system of classification or taxonomy. A group of closely related species.
- temperature: A measure of the degree of hotness or coldness of an object or substance. Temperature is measured with a thermometer calibrated in one or more temperature scales. Kelvin scale temperature is a measure of the average energy of the molecules of a body.
- weather: Daily or short-term conditions like temperature, cloud cover, precipitation and wind affecting a certain area.
- adaptation: A change in the structure or function of something. In biology, a change in a species, as a result of natural selection. Individuals with a particular feature (adaptation) are more likely to survive and reproduce than individuals without this feature.
- condition: An existing state or situation; a mode or state of being.
- data: The unprocessed information we analyse to gain knowledge.
- nectar: A sugary liquid found in many flowers, made and stored in a nectary. Used to attract animals, which eat it and accidentally collect or deposit pollen at the same time.
- toxicity: The level of harm a toxin can cause.
- larva: An immature form that some animals (such as insects, crustaceans and amphibians) pass through before metamorphosing into an adult form.
- vertebrate: Animals that have a backbone, including mammals, birds, reptiles, amphibians and fish.
- invertebrates: An animal without a backbone, for example butterflies, worms, snails, insects, spiders and aquatic species such as crabs and jellyfish.
- bug: In biology, an informal term for an insect, insect-like creature, virus or other microorganism.
- larva: An immature form that some animals (such as insects, crustaceans and amphibians) pass through before metamorphosing into an adult form.
- parasite: An organism that lives in or on another organism. Parasites usually cause harm to their host organism.
- decline: The gradual and continuous loss of something such as bird numbers or sea ice.
- endangered: A species that is possibly going to become extinct soon due to limited numbers of individuals alive or not enough habitat to live in.
- entomologist: A person who studies insects, including their classification, life cycles, distribution, physiology, behaviour, ecology and population dynamics.
- citizen science: Citizen volunteers participate in scientific projects and work in partnership with scientists to answer scientific questions.
- diseases: 1. An abnormal condition of an organism that impairs bodily functions. 2. In plants, an abnormal condition that interferes with vital physiological processes.
