- Written by Nadia O'Carroll
Although it is one of Australia’s largest butterfly species (males 12-13cm wingspan and females 14-16 cm wingspan) it is best known for its beautiful colours, which are designed to be a sign of toxicity to warn away predators.
The male butterfly establishes and defends a territory, which may be up to 4 kilometres away from his birthplace. The female travels much farther because the Richmond Birdwing Butterfly larvae is adapted to feed on only two vine plants – Pararistolochia praevenosa and Pararistilochia laheyana. The female butterfly locates these plant species by detecting the pheromones that these vines emit. After mating, she may fly up to 30 kilometres to reach the vines and lay her eggs.
The life cycle of the Richmond Birdwing Butterfly has four stages:
Egg - once she has located the right plant, the female butterfly uses sensors on her front legs to detect the state of the leaves, and will lay her 60 to 100 eggs on leaves that provide the best food resource for her larvae (caterpillars). The eggs hatch in 10 to 13 days.
Larva the caterpillar emerges from the egg and begins to feed on the vine leaves. In order to grow the caterpillar must split out of its skin, this moult may occur four to six times; each stage is described as an instar. When the final instar stage is reached the larva is ready to pupate.
Pupa (chrysalis) when the caterpillar is fully grown, it makes a silk pad which it uses to attach itself to a leaf. A release of hormones initiates the transformation from larva to pupa and within the skin of the pupa remarkable changes occur. These changes are effected by weather conditions, in summer adults emerge after 28 days but in winter it takes 250 days for the adult to develop.
Adult has a lifespan of 4 to 6 weeks. The adults feed on nectar, usually from blossoms of high canopy tree species but also from native and exotic flowers.
The Richmond Birdwing Butterfly is classified as vulnerable; it used to range from Maryborough to Grafton and west to the Great Dividing Range. However it is now extinct from two thirds of its former range, mainly due to the continuing destruction and fragmentation of its habitat, particularly the larva food vines. Another danger is the introduced vine Dutchman’s Pipe (Aristolochia elegans), the female butterfly is attracted to lay her eggs on this vine but unfortunately it is poisonous to the larva.
It is hoped that efforts to plant corridors of the larva’s food vines in a coordinated network may assist the recovery of the species. Everyone can help by removing Dutchman’s Pipe vine and planting a few Richmond Birdwing Butterfly vines in their garden.