Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Nymphalidae
Genus: Danaus
Species: D. petilia
Binomial name: Danaus petilia
Synonym: Danaus chrysippus, Danaus chrysippus petilia
Common name: Lesser wanderer

The lesser wanderer butterfly, Danaus petilia (Stoll 1790) stat. rev. (Lepidoptera: Danainae), reinstated as a species in 2005. See article http://onlinelibrary.wiley.com/doi/10.1111/j.1440-6055.2005.00423.x/abstract  

Danaus petilia (Lesser wanderer) is a medium-sized, butterfly widespread in Asia, Africa, some Pacific Islands and Australia. It arrives in New Zealand some years in mid-late summer by crossing the Tasman Sea on the westerly jet stream. It has now been found breeding in New Zealand with its caterpillars feeding on the swan plant.

The Lesser wanderer is a medium-sized butterfly with a wingspan of up to 70 mm. The body is black with many white spots. The wings are tawny, the upper side brighter and richer than the underside. The apical half of the forewing is black with a white band. The hindwing has three black spots around the centre. The hindwing has a thin border of black enclosing a series of semicircular white spots. Background colour and extent of white on the forewings varies somewhat across the wide range.
The male is smaller than the female, but more brightly coloured. In addition, male detainees have a number of secondary sexual characteristics. In the case of the plain tiger, these are: The male has a pouch on the hindwing. This spot is white with a thick black border and bulges slightly. It is a cluster of specialised scent scales used to attract females. The males possess two brush-like organs which can be pushed out of the tip of the abdomen.

Female Lesser wanderer
[1]

Female Lesser wanderer
[2]

Female underside.
[3]

A male Lesser wanderer
[4]   

Male underside of wing showing the pheromone pouch and brush-like organ
[5]

Lesser wanderer caterpillar feeding on milkweed.
 

Thanks to Wikipedia for text and information http://creativecommons.org/licenses/by-sa/3.0/