I have become a hammocker this year and I agree that is the best way to be safe from critters.

However I have backpacked in Arizona and in some places you can't find trees to hang a hammock from. So if I were tarping on the ground I would use my bug bivy

http://www.outdoorresearch.com/site/bug_bivy.html

under my tarp. I like this better than other bug netting solutions that just cover the top of your bag. Those work great against mosquitoes but not against crawling insects like ants. This one keeps me completely encased and safe from all little critters while still allowing good circulation.

Now if you are in the pines then by all means get a hammock. But otherwise consider the bug bivy.