Timing and a bit of luck is the key in getting this kind of Macro.Luck because it's not easy to find a fly salivating or as the title says "Blowing Bubble." On this capture, I timed my shot with eye on the viewfinder and waited for the fly to blow before I clicked the shutter button.
100mm Macro f/2.8 USM
Canon 430EX II Flash
3 Extension Tubes equivalent to 65mm