So many times we face an issue in macro that the subject is dark and the background is either of same color or since flash does not reach distant background, it is rendered as black.
You would agree that the photo on left is not that great since the black caterpillar is getting mixed with the background.
There is simple fix to the issue.. just pick up a leaf (or a flower if you fancy bg color) and hold it in the background with one hand. If you have a friend with you.. even better as you can ask him/her to hold the leaf for you (and return the favor by holding it when they are taking the photo). In my case I was lucky to have my friend Gauri Joshi to help with the leaf background.
Just a simple trick, nothing fancy.. but makes world of a difference.. do you agree?