Ceylon Tree Nymph
Idea iasonia, Westwood

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Ceylon Tree Nymph

The largest Danaid in the island with a wingspan of 110-155 mm. The sexes are similar. Though the male does not have sex brands, it can be distinguished from the female by its narrower forewings. Both wings are a beautiful translucent silvery white and are similar in pattern and coloration. The forewings are almost twice as long as wide. There is considerable variation in the size of the wings, their coloration and their patterns. Individuals from the dry zone are usually much larger and lighter in color than those from the wet zone. Some specimens have a reddish cast over the entire wing surface.

Similar species

Status, distribution and habitat
Essentially a denizen of the upper canopy of tall forests. Commonest in the wet evergreen forests below 2000 feet, though it is found as high as 5000 feet. Scattered colonies are also found in tall forests alongside rivers in the dry zone. A gregarious species, frequently encountered along forest streams and gravel roads through forests.

A butterfly that has truly mastered the technique of slow motion flight. Much of its time is spent hovering or sailing high up in the canopy. A large wing surface area relative to its weight allows this beautiful insect to stay afloat in the air for long periods of time without much effort, much to the dismay of photographers. Its wing beats are so slow that one may even observe the individual movements of each wing. It loves the ends of dead branches or twigs to rest on. 

Although frequently seen very high in the trees, it may be observed at or near ground level during courtship or during its visits to flowers. It has no interest in mud-sipping and does not settle on the ground. Birds and lizards keep away from this insect as it is poisonous.

Courtship is a long drawn out process; the male and female fly together for an hour or more before mating occurs. During courtship, the male extrudes his 2 pairs of hair pencils to scent the air with their pheromones and thus entice the female to land and mate. When mating does occur, it is usually near ground level, seldom in the upper canopy. 

More information about Danaids

Early stages
No records available on early stages. The closely related Tree Nymphs in South India use Agnosma cymosa as the larval host plant.

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