Which of the following statements is NOT true regarding life cycle of silk…

Concept: The silk moth undergoes complete metamorphosis through four life-cycle stages, and each stage always develops forward into the next one, never backward: egg, then larva (the caterpillar / silkworm stage), then pupa (formed when the caterpillar spins a cocoon around itself), then the adult moth (which emerges from the pupa). While spinning the cocoon, the caterpillar secretes a protein (fibroin) that hardens into the silk thread; the raw silk yarn is later obtained by reeling that very cocoon.

Application: Checking each statement against this sequence — the larvae of silk moths are indeed called caterpillars; silk fibres are the protein secreted by the caterpillar while it spins its cocoon; and silk yarn is obtained from the cocoon of the silk moth. All three match the standard sequence above. The statement "the pupa develops into caterpillar" reverses that direction: it is the caterpillar that develops into the pupa, and the pupa that develops into the adult moth — never the other way round.

Cross-check: The CTET January 2021 official Paper-II answer key marks the same option as the answer, and the NCERT Class VII "Fibre to Fabric" chapter states the identical sequence — egg, then larva/caterpillar, then pupa, then moth — confirming that this reversal is the only false statement among the four.

Result: Hence, the statement "The pupa develops into caterpillar" is NOT true, making it the correct choice.