"Maggots In Your Brains"

Context: While Lopez, an odious old miser who much neglects his beautiful young wife, Isabella, is absent from home, his wife arranges a meeting with a lover, Claudio. She fastens a string to her finger and runs it out of her apartment so that Claudio, when he arrives, can pull it and waken her. While she is asleep, Lopez comes home, discovers the device, gently disengages the string from her hand, and waits for the lover to appear on the scene. When the tug comes on the string, he gives chase to the lover, but loses him. In the meantime Isabella wakes, finds out what has happened, and bribes her maid Jaquenette to await the return of Lopez, who in the dark gives the servant a sound beating and scratches her face. He departs to get witnesses to the perfidy of his wife, as will be evidenced by the scratched face. Isabella, wholly unmarked, is there in the place of the injured Jaquenette. The witnesses ask Lopz if he is not under an illusion caused by the moon and suggest that he has maggots, or whims, in his brains, like "bats in his belfry."

Here walks my cousin full of meditation,
Armed with religious thoughts.
Is this the monster?
Is this the subject of that rage you talked of? . . .
. . .
Are not you mad, my friend? What time o' th' moon is't? Have not you maggots in your brains?
'Tis she, sure.
Where's the scratched face ye spoke of, the torn garments, And all the hair plucked off her head?