Multi-voiced, Peppered with Spanish
Because of the various narrators, In the Time of the Butterflies has a multi-voiced writing style. For example, in the first chapter, with the third-person narrator, you find lots of examples of Spanglish (Spanish mixed with English):
"And María Teresa, ay, Dios," Dedé sighs, emotion in her voice in spite of herself. "Still a girl when she died, pobrecita, just turned twenty-five." (1.1.31)
"Ay, Dios" means "Oh, God," and "pobrecita" means "poor thing."
In the sections where Minerva narrates, in contrast, the tone is more youthful, with exclamation points ("But she wouldn't budge!"), and she calls her parents the familiar terms "Mamá" and "Papá." This combination of different writing styles give the novel the feeling that it is made up of many voices, and the Spanish that pops up every now and then reminds the reader of the setting: the Dominican Republic.