H. bolina is a black-bodied butterfly with a wingspan of about. The species has a high degree of sexual dimorphism. The female is mimetic with multiple morphs.
Male
The upperside of the wings is jet black, offset with three pairs of white spots, two on the forewing and one on the hindwing. These spots are surrounded by purple iridescence. In addition, the upperside of the hindwing bears a series of small white dots.
Female
The upperside of the wings of the female is a brownish black and does not have any spots like those of the male. The edges bear white markings which are similar to those of the common Indian crow.
H. bolina is a fairly common butterfly found in lightly wooded country, deciduous forests, thick and moist scrub, and the greener parts of human habitats.
Mimicry
To the west the female is monomorphic, mimicking species of the oriental and Australasian danaid genus Euploea. Eastwards H. bolina is frequently polymorphic and most forms are then non-mimetic. In areas where it resembles Euploea the butterfly has usually been designated a Batesian mimic.
H. bolina is known for maternal care, with the females guarding leaves where eggs have been laid. Males are also very territorial and site fidelity increases with age. Territories that enhance the detection of females are preferred. The female hovers over a plant to check for ants which will eat her eggs. After selecting a plant which has no ants on it, she lays at least one but often two to five eggs on the undersides of the leaves.
Host plants
Race bolina breeds on Sida rhombifolia, Elatostemma cuneatum, Portulaca oleracea, Laportea interrupta, Triumfetta pentandra, and Asystasia species. Other hosts include Elatostema cuneatum, Fleurya interrupta, Pseuderanthemum variabile, and Synedrella nodiflora. They are also known to feed on Urtica dioica and Malva species.
Eggs
The eggs are a pale, glassy green with longitudinal ridges except on the top.
Caterpillar
After about four days the eggs hatch. The caterpillars immediately disperse. They are black with an orange head. The last segment is also orange. The head bears a pair of long branched black horns. The body surface is also covered with long, branched, orangish black spines. These spines look whitish and transparent immediately after moulting, but soon become the usual orange. In later instars the spiracles are surrounded by thin, dirty orange rings. Infection by Wolbachia bacteria is known to exclusively kill male specimens.
Pupa
The pupa is suspended by just one point. It is brown with a grey tinge on the wings. The abdominal segments have distinct tubercles. The surface of the pupa is rough. The butterfly emerges after seven to eight days as pupae.
Recent evolutionary changes
On the Samoan Islands of Upolu and Savai'i, a parasite had been killing the male members of Hypolimnas bolina. The problem was so severe that by 2001, males made up only 1% of the population. However, in 2007, it was reported that within a span of just 10 generations, the males had evolved to develop immunity to the parasite, and the male population increased to nearly 40%.. This evolutionary event involved changes at a single genomic region on chromosome 25, and represents one of the fastest examples of natural selection observed to date in natural populations. Ed Yong has written a popular science account of this highly unusual evolutionary event.
