The
stages (they vary in number according to species of
insect) of growth between
molts of an insect
nymph.
Instars mostly look like little adults with minor variations. They molt as they
grow but maintain the same basic body form. The instar stages are when the insect does all its growing. Insects have
exoskeletons and can't grow unless they shed their old
skin for a new one.
Contrast with
metamorphosis.