How does the poet argue that in killing the flea the girl commits triple murder? ( MEG 101 ) ( STUDY OF JOHN DONNE )

In the poem "The Flea" by John Donne, the speaker argues that in killing the flea, the girl would be committing triple murder because the flea has sucked blood from both of them and has thus become a symbol of their union. The speaker says that by killing the flea, the girl would be killing the flea, herself, and the speaker, as their blood has been mingled in the flea. The poet tries to persuade the girl not to kill the flea, suggesting that the flea's act of biting them has already consummated their union and made them one, and that this is a more important bond than any external marriage or social convention.