Leila summarizes her song by singing that fairies could not live without the activity of human lovers (72). I suspect Gilbert would like Leila to swallow the final syllable. Sullivan may have had that in mind; his music makes it easy to do so. On the other hand, Kravetz (181) suggests that the fairies "are in the habit of buzzing around people in love the way horseflies -- you get the idea. Besides, it's a rather nice play on words."
That we almost live on lover!