Hypolimnas bolina nerina (Fabricius)
A large butterfly, wide ranging from Australia through to Southeast Asia, China to India, and even on the Island of Madagascar. It is a highly variable species in its international range, occurring as a number of subspecies and forms, and even in size. The females are particularly prone to polymorphism and at least six main colour forms are recognized in Australia, and there are further intergradations between those forms. Some of these forms mimic the poisonous Euploea and Danaus butterflies. Only the typical form (photos shown on the left) has been recognised in South Australia.
When not in a migratory mood, the butterflies are usually seen flying near their hostplants.
The larvae have many hostplants. In South Australia its hostplants have not been recorded in the wild. Documented hostplants occurring interstate and which can also be found growing in South Australia are Alternanthera angustifolia (narrow-leaved joyweed), A. denticulata (lesser joyweed) (Amaranthaceae); Dipteracanthus spp, *Ruellia spp (Acanthaceae); *Modiola caroliniana (red-flowered mallow), Sida spp (Malvaceae); Persicaria prostrata (trailing knotweed) (Polygonaceae); *Galinsoga parviflora (yellow weed) (Asteraceae). In captivity, larvae will also eat plants in the Urticaceae Family (stinging nettles). In Malaysia and recently documented from Queensland, females will also use sweet potato (*Ipomaea spp, Convolvulaceae). The larvae will eat most of the softer parts of the hostplants.
This butterfly is also a popular species for home breeding in captivity during summer and autumn months, and in Adelaide, joyweed is the hostplant used for this purpose. This plant can be locally common in the region.
Mature larvae 50-55 mm long. In captivity, the larvae develop through 7 instars.
21 mm long.
The butterfly is seen flying all year round in the tropical north of Australia. During summer and autumn with seasons of high humidity it will fly south, occasionally reaching the temperate areas of South Australia and Victoria. In South Australia it has been documented from February to May, but as there have been very few butterfly surveys in the Far North of the state, these flight periods will certainly be extended.
Normally a tropical butterfly with strong vagrant tendencies. It has been sporadically documented from the eastern half of the state, but more particularly from the Far Northeast. It has also been recently recorded migrating in low numbers in a southerly direction through Ernabella in the Far Northwest. Opportunistic summer and autumn breeding populations in northern areas of South Australia originate from interstate northern tropical areas after good monsoon rains, with the butterflies usually following the major creek lines down into South Australia as the receding flood waters retreat from the flood-plains allowing the butterfly's larval hostplants to proliferate. These breeding populations die out during the winter months, as their early stages cannot tolerate the frosty nights. The population adults also die out or reverse migrate to northern, frost-free areas. The butterfly is not biologically suited to the temperate conditions of southern South Australia, even though its hostplants occur.
Interested public now have access to live eggs and pupae reared in the heated butterfly houses of the eastern states, and so it is likely additional random recordings will continue to occur in future years.
The butterfly normally requires tropical, humid woodland habitat. However, its strong vagrant tendencies takes it south into subtropical areas during the warmer months where it may set up local populations wherever its hostplants grow in adequate density. Its larval hostplants are widely distributed in the extreme Far North of the state, particularly along the ephemeral creeks of the Lake Eyre Basin and more particularly the flood plain areas of the Cooper and Diamantina-Warburton Creeks. The joyweed hostplants are also fond of growing in man-made dams. The hostplants are annuals and perennials, and are therefore dependent on rain or flooding for regeneration.
A vagrant. Common in the north of Australia.
No major threats. However, its preferred hostplants in the north of South Australia are dependant on semi-permanent waterholes along the major ephemeral creeks or on their floodplains, and most of these waterholes are on pastoral leases and consequently the plants are likely to suffer from cattle trampling.