Brown Hairstreak
Thecla betulae
The brown hairstreak is a butterfly in the family Lycaenidae. The range includes most of the Palaearctic. Source
Where it is now
In the last 8 weeks this insect was recorded 86 times across 5 areas (each area is a 5 degree square).
See the Brown Hairstreak on the live map
Movement and weather
Over the weeks it was present in the past year, its centre in Europe ranged from 48°N in December to 60°N in August, about 1,400 km apart.
Arrival dates
The week it was first heard regularly in each region, after at least six weeks away. Dates differ from south to north, so a region has a range.
| Region | First arrival | Last arrival | Typical peak | Areas |
|---|---|---|---|---|
| Europe | 17 November 2025 | 20 July 2026 | 10 August 2026 | 3 |
Figures are effort corrected and come from automatic sound identification, which makes mistakes. How this is measured and how it compares with human observers.