Which process directly triggers the pupal stage during insect metamorphosis?

💡 Explanation

When ecdysone secretion exceeds juvenile hormone levels, the prothoracic gland stimulates molting by secreting ecdysone, but the absence of JH commits the larva to pupation. Therefore pupation results, rather than larval molting, inhibition of growth, or oxygen regulation which have different signaling mechanisms.

• Which process limits the ability of a lepidopteran larva to regenerate a lost limb during molting?
• Which mechanism maintains consistent respiratory function for birds undergoing highly variable wing kinematics?
• Which airflow outcome enables prolonged soaring flight because of vulture feather alignment?
• Which risk increases as bird flight speed elevates without compensating air sacs?
• Which outcome occurs when increased atmospheric back-pressure impacts plant transpiration?
• Which feedback response decreases transpiration rate when abscisic acid concentration elevates rapidly in xylem sap?