One of the loveliest sights in the summer garden is the monarch butterfly gracefully flying around. They are so beautiful they are considered the ‘king’ of butterflies, hence the name monarch. Their Maori name is kākahu, meaning cloak.
Monarch butterflies are native to the United States where they exist in their millions. In the winter they make the long migration south to the warmth of Mexico and return north in the spring. Monarch butterflies were introduced here in the 1800s from California, so our butterflies do not migrate like the North American ones.
They are easily recognisable and quite distinctive, being bright orange with black wing veins. The outer, black wing border has white spots while the upper corners of the top wings have orange spots.
Although they look similar, you can tell the males and females apart by looking carefully at their wings. The males have a black scent gland spot at the centre of each hind wing, along one of the thin black veins. Females have darker veins than the males and lack the black scent spot. Males deposit a yellow, sweet, honey-scented fluid from their anal glands into their scent spots; from there, the scent can be released to attract females for mating.
Monarchs lay their eggs on milkweed plants such as the swan plant (Gomphocarpus fruiticosa). The eggs are dome-shaped and ridged and a female can lay several hundred, after which she dies. It takes between five and 14 days for the eggs to hatch. The caterpillars are quite distinctive, yellow with black and white stripes. If you are watching the caterpillars develop, try not to handle them, as they are quite delicate and you could injure them.
The caterpillars feed ravenously for about two weeks, growing large in the process. When feeding, the caterpillars ingest toxic substances from the milky sap of the swan plant called cardiac glycosides. This makes the caterpillars toxic. In spite of this protection, and their bright warning colours, some do not survive and become food for the birds. I ‘lost’ a few caterpillars off my swan plant last summer and think the many birds in the garden may have eaten them, or it could have possibly been wasps, as the caterpillars’ worst predators are wasps.
After about two weeks the caterpillars are ready to make a chrysalis. The transformation from caterpillar to butterfly takes another two weeks, depending on the weather. In warm weather it may take a few days less, in spring and autumn it make take a bit longer. The monarch’s scientific name, Danaus plexippus, means ‘sleepy transformation’.
The chrysalis protects the caterpillar while it metamorphoses or changes shape into a butterfly. The chrysalis is very beautiful, being a greeny-blue colour with several gold spots along the top. Biologists aren’t sure what these spots are for but think they are essential for the normal development of the butterfly.
When the butterfly is ready to hatch, the chrysalis will be transparent and the folded wings of the butterfly can be seen through it. Butterflies usually emerge from their chrysalis mid-morning if it is still and warm. The newly-emerged butterflies hang from their empty chrysalis case for a few hours to let their wings dry and harden. Then they are off, on their first flight. If you are lucky enough to see one emerge, don’t be tempted to touch it as you could damage its delicate wings!
The adult monarch butterflies feed on the nectar of a variety of flowers. Like other butterflies, monarchs have a long, coiled tongue called a proboscis that it uses to suck up nectar from the flowers it visits. They like flowers with bright colours, in shades of pink, purple and blue – our native hebes are a good source of food for them.
Those colourful black and orange wings that make the monarch so distinctive also serve as a warning to predators. Remember the toxins the caterpillars ingested from the swan plants when they were feeding? These are still present in the butterfly and are very poisonous, so any birds that are tempted to eat them will become sick and avoid eating them a second time!
Like many other butterfly species, monarchs are in decline, so we should give them a helping hand by planting swan plants for the caterpillars to eat and bright nectar-filled flowers for the adults, to help keep the monarchs of our gardens alive.