F is for Fly.
When I was eight years old, I killed a fly in Ft Pierce, Florida.
If she had lived a full life and reproduced, and her children had lived full lives and reproduced, and so forth, and so on, there would now be about 10,000,000,000,000-000,000,000,000,000,000,000,000 extra flies right now.
You're welcome.
Actually, there'd be a whole lot more than that, but there's only so many zeroes I'm willing to type to prove a point.
Flies live only about a month, if they're lucky, watch their weight, and get plenty of exercise, but in that month a female can lay 9,000 eggs. The eggs hatch into maggots which would seem adorable if you were a mama fly, and they feast on something dead or rotting until they change into flies and the wonderful circle of life begins all over again.
The adult fly eats by regurgitating a little bit of stomach acid onto its food and sucking it up through a soda-straw-like mouth part. This may explain why flies are such remarkably un-finicky eaters: everything they eat tastes like fly puke.
Flies are generally considered revolting, but they and their offspring eat a lot of nasty stuff which otherwise would be stacked up hip-deep before we knew it. Ever notice how many squirrels and birds and chipmunks you see? Bunches, right? Bunches and bunches and bunches. Well, how often have you seen one dead? Oh, sure you see a dead animal from time to time, but think about this: every animal you've ever seen, plus every animal you've never seen, dies. And yet, you only come across some poor critter's corpse once in a while. Ever wonder why? No, of course you don't, you thoughtless rapscallion, because if you did, you'd take a moment to be grateful for the relentless appetite and wondrous reproductive powers of... the fly.