Aetius v, 19, 4 gives the following account of Anaximander’s zoogony: Ἀναξίμανδρος ἐν ὑγρῷ γεννησθῆναι τὰ πρῶτα ζῷα φλοιοῖς περιεχόμενα ἀκανθώδεσι, προβαινούσης δὲ τῆς ἡλικίας ἀποβαίνειν ἐπὶ τὸ ζηρότερον καὶ περιρρηγνυμένου τοῦ φλοιοῦ ἐπ’ ὀλίγον χρόνον μεταβιῶναι. I argue that we should translate this as: Anaximander said that the first animals were generated in moisture and enclosing themselves in spine like barks, as they advanced in age they moved onto the drier and shedding their bark for a short time they survived in a different form. I argue that Anaximander’s hypothesis on the origins of life is based on the life cycle of the Caddis fly. If so, his account of zoogony is neither myth nor outright speculation, but is based on observational knowledge. This has significant implications for the nature of Anaximander’s zoogony and its relation to his cosmogony and cosmology.