Wood White performing their ritual

My favourite butterfly, the Wood White, performing what is said, to be their courtship ritual. In this photo the ritual is being performed by a male [left] and a female, [1st brood] but it is quite common to find two males performing this same ritual. So how can it be a courtship ritual?, as everyone knows males can't mate with males. I believe that there are two rituals. 1st, a very short ritual lasting a few seconds, where the male sits opposite a female and waves his white tipped antenna either side of the female and, alternately open and close their wings. This can vary with each courtship but can end in the act of copulation. 2nd, a much longer ritual, [being performed in the above photo] lasting a few minutes at a time. And is performed by males on males and, also males on females. Go to my page, Wood White butterflies of Chiddingfold Wood, 6.2.2016 for a more detailed account of this ritual and other facts on this beautiful but rare woodland butterfly. Thank you.