larva

Short definition from Wiktionary

Noun

1. 1
   An early stage of growth for some insects and amphibians, in which after hatching from their egg, insects are wingless and resemble a caterpillar or grub, and amphibians lack limbs and resemble fish.
2. 2
   An animal in the aforementioned stage.
3. 3
   A form of a recently born or hatched animal that is quite different from its adult stage.
4. 4
   A preliminary stage of someone or something, before it has fully matured, especially a time of growth rather than one of performance.