Thecla betulae
In 3 days ~10% in a week ~20%
The brown hairstreak (Thecla betulae) is a butterfly in the family Lycaenidae. The range includes most of the Palaearctic. The following description of this butterfly was written by Adalbert Seitz in 1909: Z. betulae L. Black-brown; male with a pale diffuse patch, female with a broad orange band beyond the crossveins. Underside ochreous, with dark-edged white lines. In North and Central Europe und Northern Asia eastward to the Pacific. Tutt name males without the pale diffuse patch beyond the crossveins ab. unicolor, while this patch is nearly white in ab. pallida Tutt. In ab. spinosae Gerh. there appear beyond the apex of the cell small orange-spots, which may be paler yellow than the discal spots of the female. The orange discal band of the female is sometimes narrow: ab. restricta Tutt, and sometimes broad (= ab. lata).
females in which the band is pale ochreous instead of orange are ab. fisoni Wheeler, while the band is separated into several spots by the heavily black veins in ab. lineata Tutt. A very remarkable form is ab. cuneata Tutt, which bears a broad orange submarginal band on the hindwing. On the underside the white lines are sometimes more or less... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Cévennes National Park | 🇫🇷 France | |
| 2 | Bavarian Forest National Park | 🇩🇪 Germany |
Rare
Under 5% of wildlife watchers report a Brown Hairstreak sighting in Paris on a given day, based on 5 verified sightings from GBIF citizen-science data. It is the 827th most-seen of the 916 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Brown Hairstreak in Paris on a given day, so our monthly data shows no clear season.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Brown 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.
11th of 11
Of the 11 cities where we can rate Brown Hairstreak sightings, Paris ranks 11th at under 5%. The best odds are in London (United Kingdom, about 10%), Prague (Czechia, about 10%) and Munich (Germany, about 10%).
Same family: Lycaenidae
The closest relatives of the Brown Hairstreak that you can see in Paris (family Lycaenidae, Gossamer-winged Butterflies) are Geranium Bronze (about 20%), Common Blue (about 20%) and Holly Blue (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Brown Hairstreak is recorded against all the insects logged in Paris (5 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.
