The tiny insect is the primary image of the poem, through which all the metaphors and puns that Donne is famous for are woven. He takes advantage of the contrast between the small size and general insignificance of the flea and the monumental importance that the speaker ascribes to it. Of course, this is all meant to be very humorous and witty, from the author's perspective if not the speaker's.
- Line 1: He begins the poem by directing the attention of his beloved to the flea. Donne uses the device of apostrophe by speaking to a person outside the poem who cannot respond.
- Line 8: He personifies the flea as if it were a "pamper'd" person, gorging on a feast of blood. Here we get the oh-so-delicious image of a flea swelling with blood.
- Line 10: The speaker uses metaphor to equate blood with life: the flea contains three lives, its own, his, and hers.
- Line 20: Oh, no! She kills the flea, but the grandiose rhetoric about "the blood of innocence" contrasts with the triviality of a dot of blood on a fingernail.