In mythology a Sicilian shepherd. According to Stesichorus (ap Aeliean VH 10.18) and Timaeus (ap Parth. 29) he was son or favourite of Hermes, and loved by a nymph, Echenais, who required of him that he should be faithful to her. this he was, til a princess made him drunk and so won him to lie with her. Thereupon the nymph blinded him; he consoled himself by making pastoral music, of which he was the inventor, or it was first invented by the other shepherds, who sang of his misfortunes; the langauge of our sources is ambiguous. But Theocritus 1.66ff. tells allusively a different story. In this, apparently Daphnis will love no-one, and Aphrodite to punish him inspires him with a desperate passion. Sooner than yield to it he dies of unsatisfied longing, taunting and defying her to the end, mourned by all the inhabitants of the country, mortal and immortal, and regretted by the goddess herself.That's two stories, right there. But there are other: in a drama by Sositheus (which we have second-hand), Daphnis is in love with the excellently-named 'Pimplea' and she with him, when disagreeably for both of them she is kidnapped by pirates. Daphnis chases after her, and when he finds her she is a servant in the court of King Lityerses. This king has the habit of challenging strangers to a crop-mowing contest (which he invariably wins), killing the loser. Daphnis agrees, but his pal Herakles, taking pity on him, competes in his place, beats Lityerses, and beheads the king with his mowing scythe. He then gives Pimplea back to Daphnis, and they live happily ever after. Or else there is Longus, and his novel Daphnis and Chloe in which the boy and girl are foundlings, raised by shepherds, fall in love, and stay chaste only through their ignorance of the mechanics of lovemaking. Both are kidnapped, and endure many trials before reuniting in the end.
'Daphnis' means the bay-tree. If I had time, and inclination, I'd develop a reading that explored the extent to which this myth encodes a general puzzlement about vegetative sex. We know how humans enable their generational fecundity: shagging. We can see that this is how goats, sheep and cows do it too. But how do plants do it? It's a puzzle. In other words I'm suggesting that reading Theocritus' Idyll 1 as a hymn to human chastity misses the point: it's soaked in sex, but of a weird kind where, though desperate with sexual desire, and egged on everyone around him, including eager-and-willing females -- and, it seems, nothing loath himself -- Daphnis shags not, neither is he shagged, and so dies. The poem addresses him: 'you used to be called cowherd, but now you are like the goatherding man/The goatherd, when he sees how the she-goars are mounted/wastes away in his eyes because he was not born a he-goat. And you, when you see how maidens laugh,/you waste away in your eyes because you are not dancing with them' [Theocritus Idylls 1:86f]. The implication of the 'as x, so y' shape of this rhetorical comparison is that Daphnis is not of the same species as the dancing human females. Manifestly this is wrong (for Daphnis is a man); but latently it's true, because Daphnis is an embodiment of vegetation.
What it looks to, I think, is a not wholly coherent belief amongst the ancients that vegetative sexuality was expressed via the death of the plant. Crops are mowed, John Barleycorn must die, not only to feed us but in some sense in order than new crops can grow up, and John Barleycorn can live again. Theocritus is troping the whole vegetative world of Nature in this sexualised, passive and death-fixated manner.