The term 'stage between larva and imago' refers to the PUPA stage, which is a four-letter word. The PUPA stage is an intermediate stage in the life cycle of many insects, such as butterflies and moths. During this stage, the insect undergoes metamorphosis, transforming from a larva into an adult imago. This stage is characterized by the insect's body becoming encased in a protective cocoon or chrysalis.