This is quite awesome.
Great effort.
If you've ever played Metroid Prime, you may remember parts where the space pirates talk about the fact that the metroid leaves no definable marks on it's victim. Also, the victim never misses any organs, fluids, bones, or any other tissue; the corpse remains intact.
Not trying to be a ballbuster here, just thought I'd comment about this, since no one else seemed to.
Nice work on creating your own story for how these work though. And great art. Keep it up.