There are several characteristics of the butterfly which make it a potent symbol for the Mirabel sisters. As they face the violent consequences of a brutal dictator's rulership, as well as strife within their own home, they desire freedom. True freedom, it can be argued, requires both liberation and transformation. People must be free to make choices and access what they need as well as grow and evolve into stronger, happier versions of themselves. The butterfly reflects this sentiment very well. A butterfly starts out life as a caterpillar and, through a period of struggle and change, transforms into a butterfly. This new state of being affords the caterpillar the ability to fly: the ultimate gesture of freedom. A butterfly grows, changes, and soars on its own terms. This natural life cycle is emblematic of freedom and is perhaps why the sisters choose the butterfly as their unifying image. It is also traditionally perceived as a feminine creature, by virtue of its beauty and delicacy. This poses a striking contrast to the masculine, patriarchal nature of the oppression the sisters face. As women seeking, craving freedom, it is fitting that the butterfly should resonate with them as it does.

The Mirabel sisters choose the butterfly, la mariposa, as their symbol because they see it as a symbol of freedom and independence, which is the goal of their struggle: independence for their country, the Dominican Republic, from the horrific dictator Trujillo. Trujillo was an evil, murderous lech, a known rapist, and the murderer of 30,000 Haitians, among other things. Three of the four "Mariposas" are ambushed and killed by Trujillo's henchmen at the end of Alvarez's novel. The recollections of the fourth sister, Dede, who survived, provide the first-person account of her and her sisters' struggles, upon which the book is based.