Captured this blue this morning. To the eye it looked a lighter blue but I checked my white balance setting and I'm happy this must be a faithful rendition. Unfortunately it flew off without giving me a view of the underwing!
I tried both my field guides looking for a blue with the following characteristics:
* white margin not chequered
* small black spots inside the hind wing outer margin
* black lines extend from forewing costa a short distance along veins
* forewing has dark area like a sex brand.
I came up with nothing. I decided to ignore the dark areas because they could be caused by the sun falling at an odd angle and came up with Plebejus hespecirus (Spanish Zephyr Blue). Problems with this - Collins describes the male ups as bright turquoise blue and that isn't the colour here.
Various chalk hill blues have the spots but they have chequered fringes. The only other possible I could find was Polyommatus golgus (Nevada Blue) but that has a narrow range horizontally (Granada) as well as vertically (2500 - 3000 m) and this was in Madrid and only at 1500 m!
Finally in desperation I also considered Agrodiaetus escheri (Escher's Blue). Collins shows it with the dark areas on the forewing as in my specimen but no black spots except on subspecies dalmaticus, which is way out of range. Then intriguingly I found this
The first two photos showing upper wings and photographed in the Spanish Pyrenees do show black spots not unlike my specimen. However, escheri has slight chequering on the hind wing. When I look again closely I can almost convince myself that my specimen has a couple of black streaks in the fringe at the top of the photo and on the left hind wing.
Can anyone help me sort this out?
I think I would personally plump for Escher's as it possibly ticks the most boxes but I'm bothered by those black spots and I don't know if the website above can be trusted.
I've just discovered in my Collins a subspecies of the common blue, ssp celina, which has black spots on teh hind wing, so now I'm even more confused.
This looks as though it's a Silvery Blue Butterfly (Glaucopsyche Lygdamus) which are an endangered species and do have black spots on the hind wings. The females are a darker blue with a wider border seperating the white fringe from the rest of its wings and the underside for both sexes is a gray/brown colour. Their wing span can reach up to 3.2cm.
I was very pleased to receive a suggestion from somebody about this butterfly so I rushed to my field guide looking for Silvery Blue or Glaucopsyche lygdamus but I couldn't find it. So I Googled the species and discovered it, but it is a native of North America, so unless it hitched a ride on an Iberia long haul I am going to have to discount this idea.
You will see that I discounted the chalkhill blues because there is no sign of a chequered fringe. Also, the chalkhill blue has a broad dark band around the costa of the forewing which this one does not. Finally, Madrid is somewhat south of the published range for this species (though mu two guides don't completely agree what the range is).
I'm beginning to favour common blue, ssp celina because it is smack in range and looks like the drawing in my Collins.
Yes, probably the best option if it has all of the features in your photo and you live within range of it, were you able to sex it? Sorry if i caused any further confusion.
Tis an Escher's Blue I had a great deal of trouble working it out on the North side of the Pyrenees
Thanks. I am interested to know whyyou are so sure about this butterfly. Is it a species you are familiar with or is there some other reason you decided on Escher's rather than common blue, ssp celina?
I am no expert but here, above 1500 metres in Limestone Escher's Blues have small colonies they are certainly not common. Madrid is a good 4 hour drive and 1800 metre elevation so I am no local
Without an underwing shot we will never know what you saw, I had the same problem with many other Blues, I have 11 species nearby. In my opinion the colour markings of your Blue are identical to my posted picture which shows the underwing lacking the cell spot
Thanks for the suggestions. I am in the process of joining these forums and if I get a positive ID I will report back here.