Polia nebulosa
In 3 days ~20% in a week ~50%
Polia nebulosa, the grey arches, is a moth of the family Noctuidae. The species was first described by Johann Siegfried Hufnagel in 1766. It is found in temperate Europe and Asia up to eastern Asia and Japan. It is not present in northernmost Fennoscandia and the southern parts of the Iberian Peninsula, Italy and Greece. In the Alps it is found at heights up to 1,600 meters.
The wingspan is 41–52 mm. Forewing white tinged with brownish grey; stigmata as in Polia advena and Polia tincta; submarginal line preceded by black wedge-shaped marks, with one more conspicuous before the indentation of submedian fold; hindwing dull whitish, with, cellspot, veins, and a broad marginal border smoky fuscous; — ab. pallida Tutt represents a very white form taken in Scotland, with many of the dark transverse markings obsolete; — bimaculosa Esp. is the darker grey form with blacker markings; — robsoni Collins is a strong melanic form from Cheshire in the west of England only; there are also two aberrations from East Asia, — asiatica Stgr. (= lama Stgr.) being dull grey and smaller than typical, while askolda Oberth. from Askold Island [now ssp.] is a large... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Bavarian Forest National Park | 🇩🇪 Germany |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Nizhny Novgorod | 🇷🇺 Russia | |
| 2 | Kyiv | 🇺🇦 Ukraine | |
| 3 | London | 🇬🇧 United Kingdom | |
| 4 | Moscow | 🇷🇺 Russia |
With luck
About 10% of wildlife watchers report a Grey Arches sighting in Snowdonia National Park on a given day, based on 9 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 227th most-seen of the 387 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 50%, if each day is a fresh chance.
June
In that month about 20% of wildlife watchers report a Grey Arches in Snowdonia National Park on a given day, against under 5% in August to May, the lowest months.
Between midnight and 3 am
Across all the parks we cover, that three-hour window holds the most Grey Arches sightings with a recorded time, and about half of them come between 6 am and 6 pm: it is seen both by day and at night.
Yes
Of the 2 parks where we can rate Grey Arches sightings, Snowdonia National Park has the highest daily chance: about 10%. Next come Bavarian Forest National Park (Germany, about 10%).
Same family: Noctuidae
The closest relatives of the Grey Arches that you can see in Snowdonia National Park (family Noctuidae, Cutworm Moths and Allies) are Large Yellow Underwing (about 30%), Dark Arches (about 30%) and Flame Shoulder Moth (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Grey Arches is recorded against all the insects logged in Snowdonia National Park (9 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.
