Passage 6.26.8
τρέφουσι δὲ αὐτὰ ἐπὶ μὲν τέσσαρα ἔτη παρέχοντες τροφήν σφισιν ἔλυμον, πέμπτῳ δὲ---οὐ γὰρ πρόσω βιωσόμενα ἴσασι---κάλαμον διδόασιν ἐσθίειν χλωρόν· ἡ δέ ἐστιν ἡδίστη τροφὴ πασῶν τῷ ζῴῳ, καὶ ἐμφορηθὲν τοῦ καλάμου ῥήγνυταί τε ὑπὸ πλησμονῆς καὶ ἀποθανόντος οὕτω τὸ πολὺ τῆς ἁρπεδόνης εὑρίσκουσιν ἔνδον. γινώσκεται δὲ ἡ Σηρία νῆσος ἐν μυχῷ θαλάσσης κειμένη τῆς Ἐρυθρᾶς.
They rear them for four years, feeding them millet as nourishment. In the fifth year—knowing they will live no longer—they give them green reeds to eat; this food is sweetest of all for the creature. Once it has gorged itself with reeds, it bursts from fullness, and thus, upon its death, the greatest part of the silk is found within. The island of Seria, where this happens, is known to lie in a bay of the Red Sea.