There is a thing that nothing is,
A foolish wanton, sober wise;
It hath noe wings, noe eyes, noe eares,
And yet it flies, it sees, it heares;
It lives by losse, it feeds on smart,
It joyes in woe, it liveth not;
Yet evermore this hungry elfe
Doth feed on nothing but itselfe.

William Strode

http://www.poemhunter.com/poem/on-jealousy/