Polyommatus thersites
In 3 days ~10% in a week ~20%
Polyommatus thersites, the Chapman's blue, is a butterfly in the family Lycaenidae. It is found in southern Europe, Morocco, Lebanon, Asia Minor, Iran and across the Palearctic to Siberia and Tian Shan. It is a small butterfly with both generation dimorphism and sexual dimorphism. For the first generation the upperside is blue with grey hind-wings and in the female a sub-marginal line of orange spots. The summer generation of the female is brown with the same sub-marginal line of orange spots while they are absent in the lighter male.
Representatives of both sexes have in the spring generation grey-colored hindwing undersides while (sandy brown in the summer generation). The underside is ochre marked with black dots circled in white and decorated with a sub-marginal line of orange spots. The forewing underside is yellow grey in summer females.
Polyommatus thersites is similar to Polyommatus icarus, but they are smaller and both sexes have no basal spots on the underside of the forewing. The larva feeds on Onobrychis species (O. arenaria, O. peduncularis, O. sativa and O. viciifolia) Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Vanoise National Park | 🇫🇷 France | |
| 2 | Cévennes National Park | 🇫🇷 France |
Rare
Under 5% of wildlife watchers report a Chapman's Blue sighting in Prague on a given day, based on 15 verified sightings from GBIF citizen-science data. It is the 470th most-seen of the 724 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.
July and August
In those months about 10% of wildlife watchers report a Chapman's Blue in Prague on a given day, against under 5% in September to June, the lowest months. Those are among Prague's wettest months, with about 80 mm of rain a month against 30 mm in February.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Chapman's 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.
Yes
Of the 2 cities where we can rate Chapman's Blue sightings, Prague has the highest daily chance: under 5%. Next come Vienna (Austria, under 5%).
GBIF citizen-science records
It is estimated from how often the Chapman's Blue is recorded against all the insects logged in Prague (15 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.
