This second pair of (poor quality) video snippets are from the Derbyshire Wye the day after. They are of male adult mayflies dancing to attract mates. Most of the females are yet to have their eggs fertilised. The main egg laying activity for the mayflies on this river begins at least an hour later.
Do you remember this post from My 2012? http://dryflyexpert.blogspot.co.uk/2012/05/happy-in-hampshire.html On that day things started much earlier on Hampshire's river Anton...
Get to know your river and it's own timekeeping. Over the years such knowledge will pay you back handsomely, again and again.