Meaning of "I shut my tongue against my fly"

Question

From Aurora Leigh:

Poor child! I would have mended it with gold,
Until it gleamed like St. Sophia's dome
When all the faithful troop to morning prayer:
But he, he nipped the bud of such a thought
With that cold Leigh look which I fancied once,
And broke in, 'Henceforth she was called his wife.
'His wife required no succour: he was bound
'To Florence, to resume this broken bond:
'Enough so. Both were happy, he and Howe,
'To acquit me of the heaviest charge of all–'
–At which I shut my tongue against my fly
And struck him; 'Would he carry,–he was just,–
'A letter from me to Aurora Leigh,
'And ratify from his authentic mouth
'My answer to her accusation?'–'Yes,
'If such a letter were prepared in time.'
–He's just, your cousin,–ay, abhorrently.

What does this mean? Is it some saying or proverb?

Answer 1

The first edition of the poem (Chapman & Hall, London, 1857) has shot, not shut:

–At which I shot my tongue against my fly
And struck him;

Subsequent editions by Chapman & Hall also have shot; the Internet Archive has the third (1857) and fifth (1860) editions. It was in the early U.S. editions, for example C. S. Francis & Co., New York (1857) that the word was changed to shut.

Almost certainly shut is a misprint, because the change makes nonsense of the line, while the original version is quite clear: it is a metaphor in which the writer of the letter (Lady Waldemar) imagines herself a frog shooting out her tongue at a fly and striking it (‘him’). In the metaphor the fly stands for Romney Leigh, whom she has caught in her trap.