Daphnis was a hero from the island of Sicily. His father was Hermes, god of merchants and thieves, and his mother was a Sicilian nymph who was tricked by Hermes into making love to him. When her time came and Daphnis was born she abandoned him to die in a grove of
laurels (whence his name) on the Mountain of Hera, to avenge herself on his father.
But Hera saw her and took pity on the beautiful infant. She made sure that he was found by some shepherds, who brought him home and raised him as one of their own. From an early age he was renowned for his beauty, and for his delightful songs about the shepherd's life. His great pride were his herd of cattle, which were of the same stock as those belonging to Helios, the sun god, and of which he took the greatest care.
Many were those who desired and courted this beautiful boy. He was a beloved of the god Apollo himself, and also of Pan, who taught him to play the pan-pipes. As he grew older it was his turn to fall in love.
One day while tending his herd of magic cattle he caught a glimpse of a lovely nymph, Nomia by name, bathing in the river and fell in love with her. At first she ran off, angry to have been seen by human eyes. He did not give up and kept chasing her. In the end she relented, but warned him that if he ever was unfaithful to her she would strike him blind.
He meant to respect her wish, but one day Nomia's rival, another nymph by the name of Chimaera, plied him with wine and then seduced him. The furious Nomia took away his eyesight in revenge, and Daphnis spent the rest of his short life on earth playing the flute and singing his songs which were now sadder and even more beautiful than before.
Soon afterwards Hermes found out about his son's misfortune, and came to take him up to Mount Olympos. As he flew off he struck the rock with his foot, causing clear water to gush forth. That spring, close by the town of Syracuse, is said to flow to this day and still carries the name of the blinded youth. There the Sicilian shepherds came everafter to offer sacrifices to their hero.
Source: Robert Graves Greek Mythology, Diodorus, and Aelian's Varia Historia