Screwworm

Screwworm

Castniomera atymnius

Daily sighting probability ~10% · With luck
at Parque Natural Metropolitano

In 3 days ~20% in a week ~30%

10 Verified sightings at Parque Natural Metropolitano From 2019 to 2026
145 In all 12 parks
September Best month
☀️ Diurnal When it's spotted

About the Screwworm

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 →

Global Distribution

Parks Where Found

# Park Country Daily sighting probability
1 Tortuguero National Park 🇨🇷 Costa Rica
~20%
2 Gandoca-Manzanillo Wildlife Refuge 🇨🇷 Costa Rica
~20%
3 Masaya Volcano National Park 🇳🇮 Nicaragua
~20%
4 Tenorio Volcano National Park 🇨🇷 Costa Rica
~10%
5 Piedras Blancas National Park 🇨🇷 Costa Rica
~10%
6 Braulio Carrillo National Park 🇨🇷 Costa Rica
~10%
7 Arenal Volcano National Park 🇨🇷 Costa Rica
~10%
8 Corcovado National Park 🇨🇷 Costa Rica
~10%
9 Soberanía National Park 🇵🇦 Panama
~10%
10 Cahuita National Park 🇨🇷 Costa Rica
~10%
11 Manuel Antonio National Park 🇨🇷 Costa Rica
~10%
12 Parque Natural Metropolitano 🇵🇦 Panama
~10%

Cities Where Found

# City Country Daily sighting probability
1 San Salvador 🇸🇻 El Salvador
~10%
2 San José 🇨🇷 Costa Rica
~10%
3 Panama City 🇵🇦 Panama
<5%

Before you go

What are the chances of seeing a Screwworm in Parque Natural Metropolitano?

With luck

About 10% of wildlife watchers report a Screwworm sighting in Parque Natural Metropolitano on a given day, based on 10 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 47th most-seen of the 114 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 30%, if each day is a fresh chance.

When is the best time to see a Screwworm in Parque Natural Metropolitano?

March, May–June and August–October

In those months about 10% of wildlife watchers report a Screwworm in Parque Natural Metropolitano on a given day, against under 5% in April, July and November–February, the lowest months.

What time of day is best to see a Screwworm?

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.

Which relatives of the Screwworm live in Parque Natural Metropolitano?

Same order: Lepidoptera

The closest relatives of the Screwworm that you can see in Parque Natural Metropolitano (order Lepidoptera, Butterflies and Moths) are Banded Peacock (about 20%), White Peacock (about 20%) and Black Witch (about 10%), with each one's daily chance of a sighting.

Where does the Screwworm sighting chance come from?

GBIF citizen-science records

It is estimated from how often the Screwworm is recorded against all the insects logged in Parque Natural Metropolitano (10 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.

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