The term 'stage between egg and pupa' refers to the LARVA, which is a five-letter word. LARVA is an intermediate stage in the life cycle of many insects, amphibians, and other animals, occurring between the egg and pupa stages. During this stage, the organism undergoes significant morphological changes, such as the growth of legs and wings. In some species, the larval stage can last for several years before the organism enters the pupal stage.