Yeah all taken outdoors in the natural environament, the only "light bouncing" would be through the big diffuser on the speedlight on the camera.

Inverse-square law is 'exaggerated' when doing macro. If you are 30cm away from your subject and using a flashgun then 30cm beyond the subject is 1/4 of the light that you have on the subject. 60cm behind the subject is 1/16 of the amount of light. As long as you don't have anything behind the subject for 30-60cm you will get a nice black background :)

Some people don't like black backgrounds, for most of my stuff, I do.