Mantids are scary. If they were the size of cats, I think we'd be screwed.
I was already a little freaked out by them, with their too-intelligent eyes that follow you when you walk by. Then I had to go and witness this:
I was cleaning the large animal area at work the other day when I noticed three praying mantis sitting together on a fence post. Two larger ones which I assumed were females, and a smaller one, probably male. I admired them for a moment, then continued on with my work. A few minutes later, I glanced over at them just in time to see one of the females take a few steps and leap onto the other female, grasping her thorax. Soon it was a fight to the death. They grappled, biting at each other's faces and arms.
A few minutes after that, I watched the male tiptoe closer and closer to the fight, then finally hop onto the back of the attacking female and start to mate with her as she was killing (and eventually decapitating and eating) the other female. I don't know his fate, because I had to go back inside. But when I came out an hour later, only the (now engorged) victorious female remained on the fence, with a pathetic pile of shredded wings on the ground below her feet.
Nature, red in tooth and claw, indeed.