German to English Art/Literary Poetry & Literature

The text discusses a man transforming into an insect (Kafka) and here I'm not sure about entschluepfen and the last bit that it has a body that it's still not bound to?

Es ist das Insekt, das sich wandelt, das zuerst nochmals seine Entwicklungsstufen über Larve und Puppe durchläuft, bis es, ausgewachsen, diesen Stadien entschlüpft, einen endgültigen Leib gewinnt, an den es aber nicht gebunden bleibt.

It is the insect that transforms itself, that first runs through its stages of development once again through larva and pupa until it is full-grown and leaves these stages behind, gaining a permanent body to which it remains not bound however.