refers to the immature stage of some amphibians.

the stage where an animal is an immature, wingless, and often wormlike feeding form that hatches from the egg of many insects that is finally transformed into a pupa or chrysalis from which the adult emerges Testing for Water Quality

immature of its kind; especially being or characteristic of immature insects in the newly hatched wormlike feeding stage; "larval societies"; "larval crayfishes"; "the larval stage"

As early stage in life, usually before sexual maturity is reached. In amphibians, larval stages are for feeding. The animal will metamorphosize into the adult stage.