Sometimes, Mother Nature can be downright icky. Case in point: the pelecinid wasp.
As you can see, the pelecinid is a nasty-looking bugger, but before you panic, that isn't a stinger looming menacingly at the end of its tail. It's an ovipositor. You know, for laying eggs.
Which brings us to the icky part. The female pelecinid jabs its ovipositor into soil to detect beetle grubs. When it finds one, it lays an egg. When the pelecinid larva subsequently emerges from the egg, it burrows into the beetle grub, kills it, and proceeds to feast on the remains.
Moral: When you see one of these wasps, don't kill it. Because it controls the beetle grubs that devastate lawns.
Just think of all the grass seed you won't have to buy.