Selenia tetralunaria
In 3 days ~30% in a week ~50%
The purple thorn (Selenia tetralunaria) is a moth of the family Geometridae. The species was first described by Johann Siegfried Hufnagel in 1767. It is a species of both Northern Europe and Central Europe. It has a scattered distribution in Britain but is absent from Ireland.
This species is dark purplish brown, paler towards the termen, with a dark spot at the apex of the forewing. Both wings are marked with a comma-shaped white mark. The margins of the wings are angular, giving the species a distinctive shape. Two broods are produced each year and they differ considerably in size and colour. Adults of the spring brood, which fly in April and May, have a wingspan of 46–52 mm. Moths of the summer brood, flying in July and August,[1] are smaller (wingspan 44–46 mm) and darker. The caterpillar is reddish brown, mottled with darker brown, and with pale greyish.
The species flies at night and is attracted to light. The caterpillar feeds on a variety of trees and shrubs (see list below). The species overwinters as a pupa. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 3 | Pyrénées National Park | 🇫🇷 France | |
| 4 | Wadden Sea National Park | 🇩🇪 Germany |
With luck
About 10% of wildlife watchers report a Purple Thorn sighting in Snowdonia National Park on a given day, based on 11 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 185th most-seen of the 387 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
In that month about 20% of wildlife watchers report a Purple Thorn in Snowdonia National Park on a given day, against under 5% in June and September–March, the lowest months. That is one of Snowdonia National Park's driest months, with about 95 mm of rain against 240 mm in December.
Between 7 and 10 am
Across all the parks we cover, that three-hour window holds the most Purple Thorn sightings with a recorded time, and about 6 in 10 of them come between 6 am and 6 pm: it is seen both by day and at night.
Yes
Of the 4 parks where we can rate Purple Thorn sightings, Snowdonia National Park has the highest daily chance: about 10%. Next come Bavarian Forest National Park (Germany, about 10%) and Pyrénées National Park (France, under 5%).
Same genus: Selenia
The closest relatives of the Purple Thorn that you can see in Snowdonia National Park (genus Selenia) are Early Thorn (about 20%) and Lunar Thorn (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Purple Thorn is recorded against all the insects logged in Snowdonia National Park (11 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.
