Butterflies copulating overnight

Small Tortoiseshells were believed to be the only British species of butterfly that copulated overnight. Well new evidence has proved otherwise. On 29th April 2014 i found a pair of mating Orange-tips close to my home at about 5pm and they were still joined the following morning at 7am. Meaning they had been joined for at least 14 hours and, maybe a possible two more hours [my thinking is that they only parted when it was warm enough] making it at least 16 hours of mating. I have since learnt that Nigel Kitely has photographed a copulating pair of Meadow Browns that were covered in dew, which he found early morning in some long grass. Which indicates that the Meadow Browns also copulated overnight.

This pair of Orange-tips mated overnight, just like the Small Tortoiseshells

I believe that this happens when butterflies mate/join late afternoon. The sun goes in, becoming cold, so they roost where they are and stay joined overnight. The following day they go their separate ways, once its warm enough. It is thought that mating saps the males energy, which is why males tend to take in salts/minerals from Horse droppings, damp soil etc., to build-up their energy levels. Mating for the average species of butterfly probably only lasts between 40-60min. So why mate all night? As this act could well prove to be fatal to the male butterfly. Both male and female Orange-tips flew off after their marathon copulation.