In complete metamorphosis, there are four stages--egg, larva, pupa and adult. For example, in butterflies, the egg stage hatches and a larva is produced. This is the caterpillar stage. It will eat leaves and eventually, form a cocoon. Inside the cocoon, the pupa stage occurs. Here, it will grow into an adult body type and emerge. Typically, the adult and the caterpillar stage will eat different foods thus reducing competition. In incomplete metamorphosis, there are only three stages--egg, nymph and adult. This is seen in grasshoppers. The nymph is just a mini version of the adult in terms of morphology and diet. It eventually becomes a mature adult.