Species account

Ensianblåfugl (Phengaris alcon)    Denis & Schiffermüller (1775)
   Blåfugle (Lycaenidae)    ALBL    24862
Alcon Blue (gb)   Hormiguera de las Gencianas (es)   Alkonblåvinge (se)      Synonyms: [Maculinea alcon]
Measurements:
WS: 27-37mm
Generations:
1
Flight period:
JFMAMJJASOND 
SE
Identification:
Rather large. The male is anonymously plain blue above, looking like an icarus (Almindelig Blåfugl) but with a slightly broader dark rim on both wings. The female is blackish distally on both wings with a bluish patch centrally, and sometimes small diffuse black spots in the outer blue part.

Below both sexes have gray-beige base color with black spots in the discal area encircled by white; these protruding as the strongest feature on the underwing.

Worn males of amandus (Isblåfugl), without the orange half-moons on the hindwing, can be very similar to males of alcon. Whereas the female is more likely to be confused with arion (Sortplettet Blåfugl) females.
Similar species:
Life stages:
Distribution:
N Spain, C and E Europe, Denmark, S Sweden, Turkey toward Kazakhstan.
Habitat:
Heaths and moor, nutrition-poor soils, coastal grassed meadows.
Behavior:
Ant-parasitic.
Status:
In Denmark localized in western part of Jylland only. Similarly scarce in Sweden along the west coast.
Host plants:
Klokke-Ensian (Gentiana pneumonanthe) [Marsh Gentian ~ Genciana de Turbera ~Klockgentiana]
In central European mountains also:
Svalerod-Ensian (Gentiana asclepiadea) [Willow Gentian ~ Knippgentiana]

Feeding plants:
Klokkelyng (Erica tetralix) [Cross-leaved Heath ~ Brezo de Turbera ~ Klockljung]
and other common plants of the heath.
Comment:
Many subspecies listed on Finnish Maculinea.

Imago is short-lived; a few days to max. two weeks.
Alcon Blue 2032    (7 photos)
2023-07-27    Grene Sande/Gyttegårds Plantage, Denmark

Imago Han
A worn male. My first, and lucky to find it, I think, on a wet and windy day.



Alcon Blue 2122    (4 photos)
2023-08-03    Grene Sande/Gyttegårds Plantage, Denmark

Imago Hun
Egg-laying.

Only found this one animal of the species today, but compared to last time (a week ago) there were many more Marsh-gentians in bloom and I found no less than plus 200 eggs on about half the plants!

Nordens Fjärilar mentions that the underside of alcon does not have the small spot centrally of the large discal spot on the forewing underside. Here you can see one, although weak and small.




Alcon Blue 1998    (3 photos)
2023-07-27    Grene Sande/Gyttegårds Plantage, Denmark

Æg
On Marsh-Gentian [Klokke-Ensian]. This day I only found 9 eggs. A week later more than 200 were glued to the also many more flowers in blume.