Why are all Harpies female?

Looked up the Pauly at Wikisource (Paulys Realencyclopädie der classischen Altertumswissenschaft); alas, that page has not been digitised.

Looked up the Roscher dictionary (Ausführliches Lexikon der griechischen und römischen Mythologie – Wikipedia), 1884. After noting the frequent conflation of sirens and harpies, it mentions “The meaning of harpies in nature is clear enough: they are the storm clouds that the winds are married to. That meaning was still present for the older commentators: Eustathius of Thessalonica, Scholia on the Iliad. In Suda they are named as predatory demons. In allegorical treatments of myth they are courtesans who ruin any man they come near.”

So yes, the general answer is that the ancients made the equation elemental danger = female; but there was a particular template behind the harpies of wind = masculine, storm cloud = wife of wind.

EDIT: I looked up Eustathius of Thessalonica’s commentary, Iliad (that’s Saint Eustathius to you, btw); it’s a bit crabbed, but what I saw there was harpies explained as winds—that grab objects when you’re not looking. The scholia to the Iliad likewise just say that harpies are female winds, not wives of winds. So from a very superficial reading, it looks like Harpy = Stormwife is a modern, not an ancient notion.