The first is the one to which Wagner made allusion:  Jupiter has given his love to Semele.  Wickedly prompted by the jealous Juno, Semele asks her august lover to grant her a wish.  He promises that she shall have her desire, and confirms his words with the irrevocable oath, swearing by the Stygian flood.  Semele asks him then to appear to her in all his celestial splendor.  The god would have stopped her when he realized her purpose, but it was too late.  Sorrowfully he returned to the celestial abode and fearfully he put on his lesser panoply.  Arrayed in this he entered the chamber of Semele, but though he had left behind him the greater splendors, the immortal radiance consumed her to ashes.

That is one story; the other is the beautiful fable, freighted with ethical symbolism, which Apulcius gave to literature in the second century of the Christian era, though, no doubt, his exquisite story is only the elaboration of a much older conceit.  Psyche, the daughter of a king, arouses the envy of Venus because of her beauty, and the goddess’s anger because of the feeling which that beauty inspires among men.  She resolves to punish her presumptuous mortal rival, and sends Cupid as her messenger of vengeance.  But the God of Love falls himself a victim to the maiden’s charms.  The spell which he puts upon her he cannot wholly dissipate.  Hosts of admirers still follow Psyche, but no worthy man offers her marriage.  Her parents consult the oracle of Apollo, who tells him that she is doomed to become the wife of a monster who lives upon a high mountain.  The maiden sees in this a punishment meted out by Venus and offers herself as a propitiatory sacrifice.  Left alone by parents and friends, she climbs the rocky steeps and falls asleep in the wilderness.  Thither come the Zephyrs and carry her to a beautiful garden, where unseen hands serve her sumptuously in a magnificent palace and the voices of invisible singers ravish her cars with music.  Every night she is visited by a mysterious being who lavishes loving gifts upon her, but forbids her to look upon his face, and disappears before dawn.  Psyche’s sisters, envious of her good fortune and great happiness, fill her mind with wicked doubt and distrust.  A fatal curiosity seizes upon her, and one night she uncovers her lamp to look upon the form of her doting companion.  Instead of the monster spoken of by the oracle, she sees the loveliest of the immortals.  It is Cupid who lies sleeping before her, with snowy wings folded, and golden ringlets clustering about his shoulders.  Anxious for a closer view, Psyche leans over him, but a drop of hot oil falls from the lamp upon his shining skin.  The god awakes, and without a word flies out of the window.  Palace and garden disappear, and Psyche is left alone to suffer the consequences of her foolish curiosity.  After wandering long in search of the lost one, she wins the sympathy of Ceres, who advises her to seek out Venus and offer reparation.  She becomes the slave of the goddess, who imposes cruel tasks upon her.  But at length Cupid can no longer endure to be separated from her, and goes to Jupiter, who intercedes with Venus and wins her forgiveness for Psyche.  Then the supreme god gives her immortality, and she becomes forever the wife of Cupid.