It's probably not a surge, but it's a wave; women are increasingly becoming the new predator, the new serial killer. I've based my antagonists loosely in all three books in my Profiler series on real female serial killers. Dr. Deborah Schurman-Kauflin is probably first in the field to do this kind of research in her book "The New Predator: Women Who Kill." It's well-done, and it affords a view of a serial killer that--to my way of thinking--is catching on in crime fiction. All of my antagonists in The Profiler Series are females, although in the first novel the female serial killer has a sidekick; her son.