Leptotes cassius
In 3 days ~40% in a week ~70%
Leptotes cassius, the Cassius blue or tropical striped blue, is a butterfly of the family Lycaenidae. It is found in North America in Florida including the Keys, Texas south through the Caribbean, Mexico, and Central America to South America. Strays have been found in New Mexico, Kansas, Missouri, South Carolina, North Carolina and Virginia.
The wingspan is 20–35 mm. The butterfly species has an important role in Marisha Pessl's 2006 novel Special Topics in Calamity Physics. The protagonist, Blue van Meer, is named in honor of the Cassius blue. The caterpillars feed natively on Fabaceae. Food plants on record are Amorpha crenulata, woolly rattlepod (Crotalaria incana), Galactia regularis and lima bean (Phaseolus lunatus). It can also successfully develop feeding on Cape leadwort (Plumbago auriculata) or doctorbush (P. scandens), which (among the eudicots) are not closely related to its usual food plants. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Blue and John Crow Mountains National Park | 🇯🇲 Jamaica | |
| 2 | Everglades National Park | 🇺🇸 United States | |
| 3 | Iguazú National Park | 🇦🇷 Argentina | |
| 4 | Big Cypress National Preserve | 🇺🇸 United States | |
| 5 | Ría Lagartos Biosphere Reserve | 🇲🇽 Mexico | |
| 6 | Iguaçu National Park | 🇧🇷 Brazil | |
| 7 | Merritt Island National Wildlife Refuge | 🇺🇸 United States | |
| 8 | Cumbres de Monterrey National Park | 🇲🇽 Mexico |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Mendoza | 🇦🇷 Argentina | |
| 2 | Porto Alegre | 🇧🇷 Brazil | |
| 3 | São Paulo | 🇧🇷 Brazil | |
| 4 | Buenos Aires | 🇦🇷 Argentina | |
| 5 | Curitiba | 🇧🇷 Brazil | |
| 6 | Rosario | 🇦🇷 Argentina | |
| 7 | Caracas | 🇻🇪 Venezuela | |
| 8 | Miami | 🇺🇸 United States | |
| 9 | Cordoba | 🇦🇷 Argentina | |
| 10 | Vitória | 🇧🇷 Brazil |
With luck
About 10% of wildlife watchers report a Cassius Blue sighting in Iguazú National Park on a given day, based on 27 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 87th most-seen of the 306 insects we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
November
In that month about 30% of wildlife watchers report a Cassius Blue in Iguazú National Park on a given day, against under 5% in March, May and July, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Cassius Blue sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
3rd of 8
Of the 8 parks where we can rate Cassius Blue sightings, Iguazú National Park ranks 3rd at about 10%. The best odds are in Blue and John Crow Mountains National Park (Jamaica, about 40%) and Everglades National Park (United States, about 20%).
Same family: Lycaenidae
The closest relatives of the Cassius Blue that you can see in Iguazú National Park (family Lycaenidae, Gossamer-winged Butterflies) are Separated Stripestreak (about 20%), Great Emesis (about 20%) and Gray-Spotted Scrub-Hairstreak (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Cassius Blue is recorded against all the insects logged in Iguazú National Park (27 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.
