As the title In the Time of the Butterflies suggests, butterflies are a critically important motif throughout Alvarez's story. The three Mirabal sisters who become directly involved in the revolution—Minerva, Mate, and Patria— are codenamed Mariposa, Spanish for butterfly. Specifically, Minerva is first codenamed Mariposa but soon becomes Mariposa #1, and Mate and Patria become Mariposa #2 and Mariposa #3, respectively.
Aside from their beauty, butterflies connote transformation through metamorphosis. The novel leans heavily on this connotation, as the sisters themselves transform over the course of the novel, both from children to adults and from naive citizens into courageous revolutionaries. Moreover, the revolution itself is attempting to transform the Dominican Republic from an unjust dictatorship into a free and fair country.
Butterflies come up in other, more specific instances throughout the story. For example, in Chapter One Dedé smuggles a butterfly orchid back from a trip to Hawaii and then accidentally cuts the flower. This act foreshadows the death of the butterflies just as the reader is becoming aware of the story's ending, which is later communicated to the reader explicitly. Furthermore, courage is often described figuratively as having "wings" throughout the novel, with characters described as if they could take flight in moments in which their courage blossoms. This makes those who are courageous, like the Mirabal sisters, capable of transcending the circumstances they were born into, metaphorically soaring like a butterfly post-metamorphosis.