Recently saw great numbers of Common Blues (I think) sitting on charcoal in old campfires in a nature reserve in Europe. Presumably they're after a mineral in the charcoal? Or is it that the blackness which attracts heat that they're after? I suppose it could be mud puddling if charcoal retains mois...

Recently saw great numbers of Common Blues (I think) sitting on extinguished campfires in a nature reserve in Europe. Presumably they're after a mineral in the charcoal? Or is it that the blackness attracts heat? No other butterflies nearby seemed to care. I suppose it could be mud puddling if charc...