True.A longish lens might be nice as you'll avoid frightening the beasties... and stay far enough from them that they don't feel the need to come a GET you!....
What's a really good macro lens to have ?
I have a Siggy 150mm f2.8 and I think it's wonderful.
Don't knoiw about the Sigma's mentioned above but I have the Tamron 90mm f2.8 Di and am very pleased with it on a D300. It is a sharp lens and good for both flowers and insects at that focal length
This was shot earlier this year with it.
Lilly by Don't like to be Bored, on Flickr
HTH
Nick
Nikon 105 is probably the best, if not the Tamron 90mm is very close!