larva
n.the early stage of an insect's life before it turns into an adult. It looks very different from the adult and usually eats a lot to grow.
n.the immature, worm-like stage of an insect or other arthropod, typically occurring between the egg and the pupa or adult stage.
“The caterpillar is the larva of a butterfly.”
“The mosquito's larva lives in the water, feeding on organic matter until it is ready to emerge as an adult.”
“In many species, the larva undergoes several molts as it grows, eventually forming a pupa before the final transformation into a winged adult.”
“These chemicals transform the cells into an abnormal growth that feeds the larva while robbing the plant of nutrients.”
From Latin larva (“disembodied spirit, ghost, goblin”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.