why are the mirabal sisters connected to butterflies?

Butterflies do not start out as the colourful flying creatures that we think of. They begin as a chrysalis confined in a cocoon and undergo a transformation known as metamorphosis. The Mirabal sisters are like this too. Under the oppressive Trujillo regime, most people, including the Mirabal sisters, felt confined. Upon realizing the truth about this dictator, Minerva and her other sisters begin to fight the order of things are transformed. Indeed, Minerva's alias becomes the "butterfly" and we see this enclosed woman break free from the shackles of "El Jefe". There is ,in the end, a heavy price to be paid by all the sisters for spreading their wings showing their beautiful colours, but the effect is lasting. All except one are silenced but like the butterfly, their beauty lasts and transforms a country.