Rosko, Mongo has taken almost identical shots some years ago at that time using a D200 and Nikon 200-400 VR1. It worked very well.
When it is too difficult to get close enough with a smaller or macro lens for these subjects, then, the long lens is, at least, one way of overcoming that difficulty. One of the only ways to get these subjects and similarly small subjects in flight, is to pre-focus on an area they must fly past to get to the flower and then exercise a ridiculous degree of super human patience.