Species account

Foranderlig Blåfugl (Plebejus idas)    Linnaeus (1761)
   Blåfugle (Lycaenidae)    IDBL    24866
Idas Blue (gb)   Esmaltada Sencilla (es)   Hedblåvinge (se)      Synonyms: Foranderlig Blåvinge (se)
Subspecies
idas
altarmena
Forster (1936) - Armenia and ?
Measurements:
WS: 21-28mm
Generations:
1
Flight period:
JFMAMJJASOND 
SE
Identification:
Can be difficult to separate from argus (Arugsblåfugl).

The male above shows a narrower and more well-defined black rim to both wings and a narrower white edge. The distal part of the ribbons is black. The female is brown and blue above with orange crescents filled with black spots along the outer margin of both wings.

Below the male is paler than the female, and shows a bluish cast toward the body, but much less so than argus. Both sexes show the same pattern as argus with submarginal orange spots(band) bordered distally with 3-6 bluish glittering spots and proximally with black arrows and white wedges. The black spots within the wedges are normally larger and more round than on argus (though, I'm not sure this is always a reliable field mark).

Idas does not have the amber-colored tag on the front leg that argus has (magnification necessary to see this in the field).
Similar species:
Life stages:
Distribution:
Europe, Turkey, Middle East, Asia and N America.
Habitat:
Meager soil. Heaths, sandy coasts, mountain slopes, bogs and moors.
Behavior:
Seeking higher elevation roosts than argus.
Status:
Scarce in Denmark. Mostly Jylland and small adjacent islands. Also N and C Sjælland, Møn and Bornholm. Widespread Fennoscandinavia.
Host plants:
Almindelig Kællingetand (Lotus corniculatus) [Bird's-foot Trefoil ~ Loto Corniculado ~ Käringtand]
Mose-Bølle (Vaccinium uliginosum) [Bog Blueberry ~ Arándano Negro ~ Odon]
Hedelyng (Calluna vulgaris) [Heather ~ Brecina ~ Ljung]
Engelse Visse (Genista anglica) [Petty Whin ~ Gatiña ~Nålginst]

Sweden:
Gyvel (Cytisus scoparius) [Common Broom ~ Retama Negra ~ Harris]
Comment:
Ant symbiosis.
Subspecies mentioned for N Sweden and Norway lapponica
Idas Blue 982    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago
Probably a female with the dark base color.



Idas Blue 978    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago




Idas Blue 854    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago
Very worn male with mating pair 853 in the background.

I guess these worn animals are impossible to identify since Silver-studded Blue also can be seen at this locality. But the fact that all identified animals look like Idas, I assume that these are too. At least it's nice to have them as a reference.




Idas Blue 1744    (1 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago
Bogs near Skørping.



Idas Blue 977    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Han
With large spots on the frontwing.



Idas Blue 984    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Han




Idas Blue 983    (2 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Han




Idas Blue 981    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Han




Idas Blue 866    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han




Idas Blue 877    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han




Idas Blue 862    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han
Semi-worn still allowing to see the well-defined black border, including on the front edge of the forewing, which silver-studded normally doesn't show.



Idas Blue 864    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han
The black border is thin but does look a bit blurry at the edge, but probably not enough to justify to suspect that it could be a silver-studded.



Idas Blue 858    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han




Idas Blue 855    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han




Idas Blue 1749    (2 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Han
Bogs near Skørping.



Idas Blue 1748    (1 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Han
Bogs near Skørping.



Idas Blue 1745    (1 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Han
Bogs near Skørping.



Idas Blue 1743    (1 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Han
Bogs near Skørping.



Idas Blue 976    (1 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Hun




Idas Blue 979    (2 photos)
2022-06-25    Holmegaards Mose, Denmark

Imago Hun
With some bluish color on the upperside, though very dark.



Idas Blue 859    (2 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Hun
Nordens Fjärilar - Bo Söderström, mentions that the black spots inside the orange band on the hindwing are bigger and rounder on this species compared to Silver-studded.

The spots on this individual look big but the large one in the center has an almost pointed appearance proving the variation of this character, which might not be completely bullet-proof.




Idas Blue 856    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Hun
Typical female with bluish cast to upperside.



Idas Blue 863    (2 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Hun
The two upperside animals are different, but I can't remember if the underside female in the background on photo 1 is the same as the one in photo number 2.



Idas Blue 865    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Hun
Female type. The black spots on the hindwing inside the orange band are small which, according to Nordens Fjärilar, indicate a silver-studded, but they also look nice round, and combined with zero observations of proven silver-studded this day, I decided to call it an Ida.



Idas Blue 1746    (1 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Hun
Bogs near Skørping.



Idas Blue 1747    (2 photos)
2023-07-08    Rold Skov (midtjylland), Denmark

Imago Hun
Bogs near Skørping.



Idas Blue 853    (1 photos)
2022-07-03    Ulvshale (Møn), Denmark

Imago Han & Hun
Mating. Male to the left.