HYLAS, in Greek legend, son of Theiodamas, king of the Dryopians in Thessaly, the favourite of Hercules and his com panion on the Argonautic expedition. Having gone ashore at Kios in Mysia to fetch water, he was carried off by the nymphs of the spring in which he dipped his pitcher. Hercules sought him in vain ; and ever afterwards, in memory of the threat of Hercules to ravage the land if Hylas were not found, the inhabit ants of Kios every year on a stated day roamed the mountains, shouting aloud for Hylas (so Apollonius Rhodius I. I207 et seq., and later authors). But, although the legend is first told in Alexandrian times, the "cry of Hylas" occurs long before as the "Mysian cry" in Aeschylus (Persae, 1054) ; and in Aris tophanes (Plutus, 1 12 7) "to cry Hylas" is used proverbially of seeking something in vain.