"Let me give in to my most intimate pleasure and lust... then you can cut my head off and eat me"
You know that's actually something of a myth (in real mantises, that is). In completely undisturbed nature, female mantises (and nearly all spiders) don't eat their mates, but if frightened, they'll start attacking anything nearby, including their mates. (They're normally solitary hunters, and there's basically a special protocol they go through to drop the female's "kill all intruders" instinct that will be overridden if the mating ritual is disturbed.)
Basically, observers disturbing the mantises while they mated caused the cannibalistic behaviors.
