What page is the concept of "The Butterflies" first introduced?

I'm not sure of the first time but here is a defining moment with this theme,

"As she was being marched down the hall, a voice from one of the cells called out, Mariposa does not belong to herself alone. She belongs to Quisqueya! Then everyone was beating on the bars calling out, Viva La Mariposa! Tears came to my eyes. Something big and powerful spread its wings inside me. Courage, I told myself. And this time, I felt it” p.238 (my copy)