Identify the three main parts of a caterpillar's body: the head, the stomach and the bottom. The head is a small part at the front of the body, the stomach (also called the thorax) is the area of the body over the first three pairs of legs and the bottom (also called the abdomen) is the area over the last six pairs of legs. All of the caterpillar's legs are underneath its body.
Find the caterpillar's head, using a close-up picture if you have one. At the front of the head, the caterpillar has a mouth, which it uses to eat vegetation. On each side of its mouth are two antennae, which gives the caterpillar its sense of smell. On each side of its head above the mouth, the caterpillar has six pairs of eyes, called ocelli. It also has a tube called a spinneret on its lower lip, which produces silk.
Identify any distinct markings on the caterpillar. Some species of caterpillar have coloration or markings to discourage predators. These can include eye spots, which are markings just behind the caterpillar's head that create the illusion their eyes are bigger than they really are. This tricks predators into thinking they are a more dangerous animal, such as a snake. The caterpillar in your picture might also have markings that help it camouflage itself or a bright color that warns predators it is poisonous.