Celastrina argiolus
In 3 days ~20% in a week ~30%
The Holly blue (Celastrina argiolus) is a butterfly that belongs to the lycaenids or blues family and is native to the Palearctic. The common name Holly blue is derived from the association of the larval stage with the Holly tree.
In India, C. argiolus is known as the hill hedge blue. The holly blue has violet-blue wings and pale silver-blue underwings with black dots. Seitz describes it: Male above shining violet blue, only the apical portion of the costal margin being minutely edged with white. The female has both wings broadly bordered with dark, the margin of the hindwing bearing vestiges of ocelli. Underside silver-white, in the disc a row of black dots, some of which are elongate, and before the margin blackish shadowy dots. Egg very flat, whitish. Larva green or brown, marked with yellowish white, bearing catenulate (chain-like) stripes on the back, on segment 7 a gland to attract ants; head brown. On Ivy, Ilex, Euonymus, Rhamnus, Robinia, Genista, Spartium, Astragalus, Rubus, Erica, Pyrus and many other plants; in Europe visited usually by ants of the genus Lasius; in June and the autumn. Pupa mostly fastened to the underside of a leaf... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Biebrza National Park | 🇵🇱 Poland | |
| 2 | Aigüestortes National Park | 🇪🇸 Spain | |
| 3 | Sierra Nevada National Park | 🇪🇸 Spain | |
| 4 | Monfragüe National Park | 🇪🇸 Spain | |
| 5 | Kiskunság National Park | 🇭🇺 Hungary | |
| 6 | Sierra de Guadarrama National Park | 🇪🇸 Spain | |
| 7 | Triglav National Park | 🇸🇮 Slovenia | |
| 8 | Cévennes National Park | 🇫🇷 France | |
| 9 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 10 | Picos de Europa National Park | 🇪🇸 Spain | |
| 11 | Mercantour National Park | 🇫🇷 France | |
| 12 | Pyrénées National Park | 🇫🇷 France | |
| 13 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 14 | Fertő-Hanság National Park | 🇭🇺 Hungary | |
| 15 | Wadden Sea National Park | 🇩🇪 Germany | |
| 16 | Ecrins National Park | 🇫🇷 France | |
| 17 | Grand Canyon National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Birmingham | 🇬🇧 United Kingdom | |
| 2 | London | 🇬🇧 United Kingdom | |
| 3 | Liverpool | 🇬🇧 United Kingdom | |
| 4 | Manchester | 🇬🇧 United Kingdom | |
| 5 | Dublin | 🇮🇪 Ireland | |
| 6 | Brussels | 🇧🇪 Belgium | |
| 7 | Budapest | 🇭🇺 Hungary | |
| 8 | Kharkiv | 🇺🇦 Ukraine | |
| 9 | Suzhou | 🇨🇳 China | |
| 10 | Copenhagen | 🇩🇰 Denmark |
With luck
About 10% of wildlife watchers report a Holly Blue sighting in Helsinki on a given day, based on 20 verified sightings from GBIF citizen-science data. It is the 280th most-seen of the 838 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 30%, if each day is a fresh chance.
May–July and September
In those months about 10% of wildlife watchers report a Holly Blue in Helsinki on a given day, against under 5% in August and October–April, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Holly 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.
42nd of 48
Of the 48 cities where we can rate Holly Blue sightings, Helsinki ranks 42nd at about 10%. The best odds are in Birmingham (United Kingdom, about 30%), London (United Kingdom, about 30%) and Liverpool (United Kingdom, about 30%).
Same family: Lycaenidae
The closest relatives of the Holly Blue that you can see in Helsinki (family Lycaenidae, Gossamer-winged Butterflies) are Small Copper (about 20%), Common Blue (about 10%) and Green Hairstreak (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Holly Blue is recorded against all the insects logged in Helsinki (20 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.
