www.ukbutterflies.co.uk

Yes, it's a courtship ritual, as described on this page (look in the "Imago" section):

http://www.ukbutterflies.co.uk/species. ... es=sinapis

And here's a video:

http://www.youtube.com/watch?v=DjqTKIZhLmQ[/video]

Cheers,

- Pete

Should have known the answer would be on this site somewhere - it usually is!

Nice video

Mike