Very interesting book by Michael Crichton. Its about this test site in some desert (The actual location escapes me) that preforms experiaments with micro cameras/computers. The computer/cameras get loose, and form swarms, and are programmed to kill prey (Hence the name) and eat it, but can't eat, being machines, so they endlessly kill, mainly by suffication. Its not just about the swarms' killings, but I can't begin to describe the plot. You'll just have to read the book
Very good book, I recommend it to anyone that likes Michael Crichton or just science fiction, or even horror stories.