Bishop is a master of words, writing with such control that it's easy to believe that every single syllable was planned. The sound of her poems has a dramatic and dreamy quality, and the subject matter of "The Man-Moth" only adds to this effect.
We have to pay really close attention to pick up on the sound patterns in the poem, but it is definitely there. Sometimes it can feel like someone beating you over the head with a consonant, but Bishop is subtle and uses both consonance and assonance to create a gentle cadence. For a great example of both forms of sound repetition, take a look at line 8: "of a temperature impossible to record in thermometers." The M, the O, and the E sounds repeat through the line.
If you pay close attention to the sounds in the poem, you'll find that Bishop isn't just playing with words and letters, she's really painting a picture with the sonic elements of her words. A great place to look for this is in the fourth stanza. Remember all those S sounds we mentioned back in the "Detailed Summary" for lines 25-27? Those soft hissing noises do a bang-up job of imitating the soft, steady hiss of the air that moves through a subway system. Bishop isn't just telling you about the Man-Moth's environment, she's creating the scene with her sounds.