There is a way to distinguish M. rubra from other species, such M. ruginodis, by photo? I have one photographed in Pyrenees years ago and still unidentified...
Yes, It's definetly difficult to tell for sure, however M. ruginodis, is significantly rarer than Myrmica Rubra.... Especially in my area. I also am a ant keeper, I have collected several different colonies that I have raised from a single queen including myrmica rubra. So I in can just tell as soon as I see them they they are Myrmica Rubra, because I have kept them in my room all my life and have done countless research! Here is some of my recent colonies! Dates on the images are wrong, btw. I should probably fix the date on my camera.
camponotus pennsylvanicus queen with larvae
Lasius Alienus colony I raised from a single queen
Fantastic assemblages of homemade ant-houses Here's my photo of some Myrmica found in north-eastern Spain mountains. In some ant forums they was unable to tell me the exact species, but if you have experience rearing them maybe you can tell me? Thanks!
Myrmica are one of the hardest to Identify species.... however from what i can see. Dark color... only a few workers.. I would say they are Myrmica lobicornis. However I am not sure if they are in Spain?