Hover Fly on Potentilla Flower,

Firstly, thank you all for the wonderful comments, stars and hearts for my Kingfisher photograph yesterday, it hit the spotlight and is featured on the favourites page too. I had such a super day with my granddaughter yesterday and to do so well was the icing on the cake.
Back to earth today and my photograph is of the hoverfly on the pretty little potentilla flowers, I have the bell flower next to this and I think the two colours go together so well. I watched the hoverfly for some time and was fascinated how they seem to pick a flower head and then head butt the stamen several times before actually landing and sucking the nectar. I wondered if this stimulated the stamen into releasing more nectar for the insect to gather.