Idea iasonia
In 3 days ~70% in a week ~90%
The Ceylon tree nymph (Idea iasonia) is a species of nymphalid butterfly in the subfamily Danainae. It is endemic to Sri Lanka. First described by John Westwood in 1848, the Ceylon tree nymph can be found in both wet and dry zones of Sri Lanka. It is the largest member of the family Danaidae in that country. It is listed as a near threatened species in the IUCN Red List.
The species was first described by English entomologist John O. Westwood in 1848, as Hestia iasonia. For several years it was considered to be only an island race of I. lynceus, a species found in eastern Asia. However the two species have differences in their wing shapes and in the male genitalia. It is of the genus Idea, and belongs to the subfamily Danainae of the family Nymphalidae. Its binomial name is Idea iasonia.
The Ceylon tree nymph has a wingspan of 110–155 mm, making it the largest member of the family Danaidae in Sri Lanka. Both its wings have similar patterns and colouration. The wings are of a translucent silvery-white colour. The forewings are almost twice as long as their width. The female is larger than the male, and the males have narrower forewings than the females... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sinharaja Forest Reserve | 🇱🇰 Sri Lanka |
More parks will be added in future updates.
Possible
About 30% of wildlife watchers report a Ceylon Tree Nymph sighting in Sinharaja Forest Reserve on a given day, based on 114 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 11th most-seen of the 117 insects we can rate there. Over three days the chance rises to about 70%, and over a week to about 90%, if each day is a fresh chance.
July
In that month about 50% of wildlife watchers report a Ceylon Tree Nymph in Sinharaja Forest Reserve on a given day, against under 5% in August, the lowest month.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Ceylon Tree Nymph sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Sinharaja Forest Reserve, in our data
Sinharaja Forest Reserve is the only park on Wallace's Line with enough records to rate Ceylon Tree Nymph sightings: about 30% of wildlife watchers there report one on a given day.
Same family: Nymphalidae
The closest relatives of the Ceylon Tree Nymph that you can see in Sinharaja Forest Reserve (family Nymphalidae, Brush-footed Butterflies) are Glad-Eye Bushbrown (about 40%), Clipper (about 40%) and White Four Ring (about 30%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Ceylon Tree Nymph is recorded against all the insects logged in Sinharaja Forest Reserve (114 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
