The information of the altitude difference comes from Tom Tolman* and can only be used as a rough guide. Sometimes the Blues can also be found much further down, which we took into account when we discovered it. (e.g. in nausithous, teleius, eumedon, damon, bellargus).
* TOLMAN, TOM & LEWINGTON, R. 1997, 2008: Collins Butterfly Guide. HarperCollins Publishers, London (GB). pp 83-157.