Introduction
The subfamily Danainae, which includes the Monarchs & Tigers, Nymphs and Crows, comprises of about 190 species worldwide.
The genus Euploea is very distinctive. All of the 59 known species are dark brown in colour, and most have a double band of white spots on the underside of the wings, and tiny white spots on the sides of the thorax. On the upperside, males of most species have a deep blue or purple sheen, but in Euploea core the upperside is similar to the underside and lacks any sheen.
Euploea core is distributed from India and Sri Lanka to south China, and via the Malay peninsula to Sumatra, Borneo, Sulawesi, Java, Bali, New Guinea and Australia.
Habitats
This species can be found in a wide variety of lowland habitats including tropical rainforest, dry woodland, Acacia scrub, beach hinterlands, parks and gardens.
Lifecycle
The eggs are laid singly on the buds of the larval foodplants. A wide variety of plants are eaten by the caterpillars including Ficus, Streblus, Nerium, Ichnocarpus, Hemidesmus, Cryptolepis, Carissa, Toxocarpus, Allemanda, Parsonsia, Plumeria, Rhyncospermum, Asclepias, Hoya, Trachelospermum Calotropis, Gomphocarpus, Brachystelma, Marsdenia, Sarcostemma, Cryptostegia, Gymnanthera, Secamone, Stephanotis, Tylophora, Adenium, Mandevilla, Cynanchum, Leichartia and Gunnessia.
Adult behaviour
Males are often seen imbibing moisture from patches of damp ground. They also visit decomposing fruit on the forest floor, and in Sri Lanka I have seen clusters of males feeding on juices exuded by dead snakes. They also visit Senna and other leguminous plants to imbibe pyrrolizidine alkaloids oozing from the stems and seed pods. These alkaloids are processed by the butterflies to produce toxins which confer them with protection against insectivorous birds. Females are more commonly seen when nectaring, and have a strong preference for the flowers of Lantana.
At dusk the butterflies gather together in communal roosts – typically of a dozen or so will cluster together, hanging from twigs in semi-shaded situations. In the dry season, aestivating roosts of a hundred or more butterflies can sometimes be found along dry river courses in forested habitats.