The newly hatched caterpillar is yellow-green. It has a very long, black horn on the end of the abdomen. After it sheds its skin, it becomes more green. It has yellow stripes on each side of the body. There are many small white and yellow bumps on the body. After it sheds its skin a second time, the yellow stripes have blue or purple edges on them. The horn is yellow-green with the bottom part being black. After it sheds its skin for a third time, the caterpillar becomes more yellow. There is a row of black spots along each side of the body. The blue or purple edges on the yellow stripes become thicker. After it sheds its skin for the last time, it becomes even more yellow. All of the colors are brighter. There are no longer any bumps on the body. The horn is now yellow. It points downward. The horn has many little bumps on it. It will reach a length of about 13 cm (5.1 in).