I have the Nikon 105VR, and it is great both for Macro and as a general use short telephoto.
For bugs, a longer lens is better as you don't have to be in their face to shoot them. I would go to a 200 for nasty bugs, but long is good even for benign ones as they are less likely to be scared away.
At the budget end, tubes are an excellent way to go. Add them to almost any other lens. I have a Set of Kenko Tubes, and they work well with everything except the 18-200. They work on this too, but changing the focal length does strange things to the focus.
Another budget option is to reverse couple two otherwise ordinary lenses. I used to get excellent results with a 135mm reversed and taped to a 55mm lens (This was on a Pentax Spotmatic-F). Just attach one lens to the camera as normal, and tape the front of the second lens to the front of the first so that the objectives are looking at one another. You used to be able to get reversing rings to do this, but I found gaffer tape worked just as well. On
modern lenses, you may need to fudge the second lens to get the diaphragm open.