Glaucopsyche alexis
In 3 days ~20% in a week ~40%
Glaucopsyche alexis, the green-underside blue, is a butterfly of the family Lycaenidae. It is found in the Palearctic. The butterfly flies from April to July depending on the location, lingering in warm, lush meadows with plenty of its host plant, vetch (Vicia).
Male above light cyaneous blue with a violet sheen and narrow black border; female darker blue with the black border gradually shading off, so that it occupies nearly the whole outer half of the wings. Beneath silver-grey (male) or ashy grey (female), the forewing with 5 or 6 large rounded black spots, the hindwing with small ocelli and in its whole basal half with metallic blue-green dusting. In ab. dimus Bgstr. the ocelli of the forewing beneath are reduced to 4; on the other hand, they may also be increased in number, or may be elongate (= subtus-radiata Oberth.). In European Turkey and the neighbouring districts of Anterior Asia the ocelli of... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Mercantour National Park | 🇫🇷 France | |
| 2 | Cévennes National Park | 🇫🇷 France | |
| 3 | Pyrénées National Park | 🇫🇷 France | |
| 4 | Sierra de Guadarrama National Park | 🇪🇸 Spain | |
| 5 | Bavarian Forest National Park | 🇩🇪 Germany |
With luck
About 10% of wildlife watchers report a Green-Underside Blue sighting in Sierra de Guadarrama National Park on a given day, based on 18 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 182nd most-seen of the 597 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
May
In that month about 20% of wildlife watchers report a Green-Underside Blue in Sierra de Guadarrama National Park on a given day, against under 5% in June to March, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Green-Underside Blue sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 5 parks where we can rate Green-Underside Blue sightings, Sierra de Guadarrama National Park ranks 4th at about 10%, level with the leaders once rounded. The best odds are in Mercantour National Park (France, about 10%), Cévennes National Park (France, about 10%) and Pyrénées National Park (France, about 10%).
GBIF citizen-science records
It is estimated from how often the Green-Underside Blue is recorded against all the insects logged in Sierra de Guadarrama National Park (18 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.
