If you don't want to be eaten, then why not look like something totally unappetizing? In this caterpillar's case, it's bird droppings.

However, looking like poo isn't the only camouflage this kind of caterpillar can employ. One variety, a 2008 study says, has a hormone that controls when it changes from looking like bird droppings to looking like the leaf it lives on, which is the disguise it adopts in the last stage of caterpillar development.