In Ascaris, 3^rd moulting takes place in:

From the lung alveoli, the larvae of ascaris crawl up the bronchi and trachea that is aided by the current caused by the ciliated epithelium of the respiratory tract and are propelled into the larynx. The larvae leave the respiratory tract by means of cough and once more get swallowed. The larvae then pass down through esophagus to the stomach and localise in the upper part of the small intestine. Another moulting occurs between 25th to 29th days of infection.