Thanks for the tip Richard, as this is one I don't know, personally.
But this is interesting, and probably a new guide page is in order. Francoeur reported Formica gagatoides from Yukon Territory here:
http://entomofaune.qc.ca/entomofaune/fourmis/Fourmis-Publications/FourmisduYukon.pdf
I agree it looks like it, and if you are comfortable that this is indeed that species, I'll make the page. There are some other "Palaearctic" species that occur in the far north of the Americas.

@ Stephen. The one being carried is a naive ant that does not know the way to the destination. This is a form of recruitment for ants old enough to go outdoors, and transport for those still too young to get there on their own.

Very cool on both counts. Thank-you!

When I asked him to look at this picture, Europe's foremost expert on Formica wrote me, "Yes, from the distribution of matte and shining surfaces and scape length/head width it might well be F. gagatoides. But the picture has a too low resolution and does not allow separation from kozlovi. I am willing to determine voucher specimens. We have good comparison data of Palaearctic material."

I would add that F. kozlovi has, however, never been reported form North America, and so it seems more likely that the ants in the picture are in fact the formerly reported F. gagatoides. If specimens could be made avaialble, we could be 100% (rather than, say, 99%) certain. Is that a possibility, Stephen?

A latter update from Dr. Seifert is that the notably lighter, brown legs are typical of this ant in his experience.

I didn't collect, so we have only the photos to go on. For what it is worth, I will post an 1122 x 734 pixel image zeroing in on the body.

I can use this information for the species page...

The habitat was boreal forest, with birch, poplar, and spruce predominating. The photo was taken at Tetlit Gwinjik territorial park about 3 km from the Peel River ferry along the Dempster.