The only chance with hoverflies is really handheld, unless you find one roosting. Flash helps to freeze the action.
The smallest Hoverfly on the tiniest mountain flower I know. Very nice. Hoverflies move too quick for me to snap them (well, the ones down here in Australia). Nicely captured
Canon 1DX, 100mm f2.8L IS, handheld.
I am very happy with this image. The composition is nice, the focusing is right, DOF is adequate and the colors are nice. The problem with getting the shot was that it was very close to ground, both the flower and the fly are very small (the flower was about 10mm across) and as you say, the only option is handheld. So fast crawling on wet ground over time is quite tiresome. But when there is a reward like this in the other end, it is easy to accept the effort it took.
5DIII, 1DX, 7DII, 8-15/4L, 16-35 f4L IS, 24-70/2.8L II, 70-200/2.8L IS II, 200-400/4L IS 1.4x, Zeiss 15/2.8, 17/4L TS-E, 24/3.5L TS-E II, Zeiss 35/1.4, Zeiss Otus 55/1.4, Zeiss Otus 85/1.4, 100/2.8L IS Macro, Zeiss 135/2, 600/4L IS II