Do you know what this is? If you said, "Bird dropping," well, you're actually close. It is sometimes called the "bird dropping" caterpillar. It is, in fact, the caterpillar of the Giant Swallowtail butterfly. It mimics a bird dropping in order to fool predators. If I were a predator, I'd be fooled and I would definitely steer clear!
That unappetizing looking caterpillar is the result of a mating like this. Two Giant Swallowtails get together to create the next generation of their beautiful kind.
If the tiny caterpillar can munch enough citrus leaves to grow to its final stage of caterpillar-dom without attracting the attention of a predator and then if it can find a safe place to make its cocoon and pupate, maybe someday it will turn into a beauty like this. And the circle of life will be complete.