A preying mantis is a woman who, while orally pleasuring a man, bites the head of the penisright when the man is about to cum, much like the female insect (preying mantis) will eat her mate after the reproduction process.
Guy 1: Dude why is there blood on your pants?
Guy 2: Because that bitch is a preying mantis, she bit the head of my dick!
Similar to Driving the big white bus, only this time you are on your knees in front of the toilet puking up your lunch, everything you had to drink in the past 8 hours and part of your small intestine. You are also swearing to God or Jesus or the Devil or whoever that you will NEVER EVER NEVER get so fucking wasted again for the rest of your life, but probably will at the next party you are invited to next weekend.