Lymantria monacha
In 3 days ~30% in a week ~50%
The black arches or nun moth (Lymantria monacha) is a small Palaearctic moth. It is considered a forest pest. The moths of Lymantria monacha have a wingspan of 40 to 50 mm. They have white forewings with black connected wavy arches which gives the moth its name. The light brown hindwings have white fringes having black spots. They also have a characteristic biscuit-coloured abdomen with a black band. Females are larger and have elongated wings.
The eggs are oval, light brown or light red. Larvae are whitish grey to blackish, with grey hairs, red and blue warts, and a dark longitudinal dorsal line which is interrupted or broadened into spots in places. Pupa is golden glossy red-brown or dark brown, with reddish hairs dorsally and rather long anal point.
White forewing with black basal spots and four sharply angulate black transverse lines, the second of which is the broadest; hindwing greyish white and grey. Abdomen light rosepink. The species varies strongly and has received the following aberrational names, nigra Fr.: The two central bands are confluent at the costal and posterior margins, forming black spots, or the whole... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Ordesa y Monte Perdido National Park | 🇪🇸 Spain | |
| 3 | Aigüestortes National Park | 🇪🇸 Spain | |
| 4 | Cévennes National Park | 🇫🇷 France | |
| 5 | Pyrénées National Park | 🇫🇷 France | |
| 6 | Mercantour National Park | 🇫🇷 France | |
| 7 | Triglav National Park | 🇸🇮 Slovenia | |
| 8 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 9 | Ecrins National Park | 🇫🇷 France | |
| 10 | Sierra de Guadarrama National Park | 🇪🇸 Spain |
With luck
About 10% of wildlife watchers report a Black Arches sighting in Pyrénées National Park on a given day, based on 66 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 141st most-seen of the 1277 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.
July and August
In those months about 20% of wildlife watchers report a Black Arches in Pyrénées National Park on a given day, against under 5% in October to April, the lowest months.
Between 10 pm and 1 am
Across all the parks we cover, that three-hour window holds the most Black Arches sightings with a recorded time, and about half of them come between 6 pm and 6 am: it is seen both by day and at night.
5th of 10
Of the 10 parks where we can rate Black Arches sightings, Pyrénées National Park ranks 5th at about 10%. The best odds are in Snowdonia National Park (United Kingdom, about 20%), Ordesa y Monte Perdido National Park (Spain, about 10%) and Aigüestortes National Park (Spain, about 10%).
GBIF citizen-science records
It is estimated from how often the Black Arches is recorded against all the insects logged in Pyrénées National Park (66 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.
