Relationship: charcoal and butterflies?

[Bob7777777777]

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 moisture after rain but it was a warm day and I don't think there would have been any dampness left. Does anyone know more about what this is all about?

All I know about charcoal is that it is mostly carbon and is very absorbent due to a very high surface area ( I assume due to its texture at microscopic levels). I can't imagine butterflies needing carbon, but I imagine they might like getting at tiny droplets of water that are being absorbed by the charcoal - but like I say, it was a hot day so this would baffle me, and there were plenty of dirt paths nearby with no mud-puddling going on. I am no scientist, and would love to know.

[Pete Eeles]

This is a duplicate of:

viewtopic.php?f=49&t=9487

Cheers,

- Pete