The caterpillar will eat the leaves and flowers of the host plant. It makes no nests. The young caterpillar is black. It has a white spot in the middle of its body. This spot is called a saddle. It mimics a bird dropping. The older caterpillar is green. It has black bands with orange spots in each of the bands. The caterpillar has a special organ called an osmeterium. It is an orange, bad-smelling organ. It is shaped like a snake's tongue. It is kept behind the inside of the head. The caterpillar releases it to scare predators away. The caterpillar will reach a length of 5 cm (2 in). The Ozark Swallowtail caterpillar is similar to the Black Swallowtail caterpillar. It is usually greener, and the black bands are usually thinner.