The Wanderer – Danaus plexippus or Monarch, shown here on Pimelea sp. – Rice Flower, is an uncommon and somewhat puzzling visitor to Victoria. According to Museum Victoria’s Butterflies: Identification and Life History:
Populations are temporary in Victoria and migrating adults recolonise Victoria annually. Two or three generations can occur if migrating adults arrive in early spring.
…. In northern Australia the food plants are widespread weeds but in Victoria Gomphocarpus fruticosus – Swan Plant is grown more as a garden ornamental.
….. It is known as the Monarch in North America where it is noted for its large, long-distance migrations to overwintering sites in California and Mexico. Some limited migration also occurs in Australia and small overwintering colonies are known from SA and near Sydney.