Castniomera atymnius
In 3 days ~30% in a week ~50%
Castniomera is a monotypic genus of moths in the family Castniidae described by Constant Vincent Houlbert in 1918. Its single species, Castniomera atymnius, commonly known as the giant butterfly-moth, was first described by Johan Wilhelm Dalman in 1824. It is known from Mexico through Central America to Venezuela.
The larvae feed on Musaceae species. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Tortuguero National Park | 🇨🇷 Costa Rica | |
| 2 | Gandoca-Manzanillo Wildlife Refuge | 🇨🇷 Costa Rica | |
| 3 | Masaya Volcano National Park | 🇳🇮 Nicaragua | |
| 4 | Tenorio Volcano National Park | 🇨🇷 Costa Rica | |
| 5 | Piedras Blancas National Park | 🇨🇷 Costa Rica | |
| 6 | Braulio Carrillo National Park | 🇨🇷 Costa Rica | |
| 7 | Arenal Volcano National Park | 🇨🇷 Costa Rica | |
| 8 | Corcovado National Park | 🇨🇷 Costa Rica | |
| 9 | Soberanía National Park | 🇵🇦 Panama | |
| 10 | Cahuita National Park | 🇨🇷 Costa Rica | |
| 11 | Manuel Antonio National Park | 🇨🇷 Costa Rica | |
| 12 | Parque Natural Metropolitano | 🇵🇦 Panama |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | San Salvador | 🇸🇻 El Salvador | |
| 2 | San José | 🇨🇷 Costa Rica | |
| 3 | Panama City | 🇵🇦 Panama |
With luck
About 10% of wildlife watchers report a Screwworm sighting in Arenal Volcano National Park on a given day, based on 22 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 52nd most-seen of the 302 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 50%, if each day is a fresh chance.
April–May and July–August
In those months about 20% of wildlife watchers report a Screwworm in Arenal Volcano National Park on a given day, against under 5% in September–October and December–January, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Screwworm sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
7th of 12
Of the 12 parks where we can rate Screwworm sightings, Arenal Volcano National Park ranks 7th at about 10%. The best odds are in Tortuguero National Park (Costa Rica, about 20%), Gandoca-Manzanillo Wildlife Refuge (Costa Rica, about 20%) and Masaya Volcano National Park (Nicaragua, about 20%).
GBIF citizen-science records
It is estimated from how often the Screwworm is recorded against all the insects logged in Arenal Volcano National Park (22 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.
