Easily the single most amazing thing I have read about animals in my entire life: Reddit page on the Emerald cockroach wasp.
Make SURE to read the comments too - they are the reason why reddit is amazing.
And you thought your sex life was bad :-)
Update (23 Dec): Here's a somewhat 'corresponding' version about plants: "Sorry, Vegans: Brussels Sprouts Like to Live, Too"
The title is from the classic song, Finite Simple Group of Order 2