The only mentioning of the concept of "larva" in JVS is this word:
{ciftoldi} = "x1 is a caterpillar (larva of butterfly or moth - not sawfly) of species x2."
However, {cifnu} = "x1 is an infant/baby [helpless through youth/incomplete development] of species x2."
I think (although it is supposed to be a naljvajvo or even a cimjvo) a semantic shift of the concept of {cifnu} since caterpillar is no more helpless than imago.
Compare stages:
With metamorphosis, e.g. butterflies:
1. sperm/ovum
2. egg
3. laid egg
4. larva
5. imago
Cangaroos:
1. sperm/ovum
2. egg
3. newborn (helpless)
slowly turning into
4. adult
Humans:
1. sperm/ovum
2. egg
3. newborn (helpless)
slowly turning into
4. adult
Tardigrades:
1. sperm/ovum
2. laid egg => fertilisation
3. newborn (full complement of adult cells)
slowly growing (via the size of cells, not their number) into
4. adult
So although {cifnu} probably can be applied to humans and cangaroos I can't see such a stage for butterflies and tardigrades. Thus, I think that such anthropomorphism in applying {cif-} rafsi to larva stage should be avoided and probably separate brivla should be used instead.