Satyrium w-album
In 3 days ~10% in a week ~30%
The white-letter hairstreak (Satyrium w-album) is a butterfly in the family Lycaenidae. A dark little butterfly that spends the majority of its life in the tree tops, feeding on honeydew, making it best observed through binoculars. The uppersides are a dark brown with a small orange spot in the bottom corner of the hindwing. The male has a small pale spot on the forewings made up of scent scales. The undersides are a lighter brown with a thin white line, the "hairstreak", which gives this group of butterflies their name. On the hindwing this streak zigzags to form a letter W (or M) from which this species gets its name. The outer edge of the hindwing has an orange border, but there is no orange on the forewings as on the similar black hairstreak and there are two short tails, the female's longer than the male's on the hindwings. Part of a group known as "lateral baskers", they always rest with their wings closed, usually at right-angles to the sun during day.
T. w-album Knoch (72 h). Above similar to unicolorous specimens of spini; the white band of the hindwing beneath commences more proximally. about the middle of the costal... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 2 | Pyrénées National Park | 🇫🇷 France | |
| 3 | Wadden Sea National Park | 🇩🇪 Germany |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Copenhagen | 🇩🇰 Denmark | |
| 2 | Novosibirsk | 🇷🇺 Russia | |
| 3 | Berlin | 🇩🇪 Germany | |
| 4 | Munich | 🇩🇪 Germany | |
| 5 | Milan | 🇮🇹 Italy | |
| 6 | London | 🇬🇧 United Kingdom | |
| 7 | Stockholm | 🇸🇪 Sweden | |
| 8 | Paris | 🇫🇷 France | |
| 9 | Helsinki | 🇫🇮 Finland | |
| 10 | Beijing | 🇨🇳 China |
Rare
Under 5% of wildlife watchers report a White-Letter Hairstreak sighting in London on a given day, based on 39 verified sightings from GBIF citizen-science data. It is the 559th most-seen of the 1504 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June and July
In those months about 10% of wildlife watchers report a White-Letter Hairstreak in London on a given day, against under 5% in August to May, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most White-Letter Hairstreak sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
6th of 16
Of the 16 cities where we can rate White-Letter Hairstreak sightings, London ranks 6th at under 5%. The best odds are in Copenhagen (Denmark, about 10%), Novosibirsk (Russia, about 10%) and Berlin (Germany, about 10%).
Same family: Lycaenidae
The closest relatives of the White-Letter Hairstreak that you can see in London (family Lycaenidae, Gossamer-winged Butterflies) are Holly Blue (about 30%), Small Copper (about 20%) and Common Blue (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the White-Letter Hairstreak is recorded against all the insects logged in London (39 verified sightings), 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.
