You might want to look in the first Chapter and at Dede's reminiscence of the family time together in the garden at night. There is one excerpt from this chapter that really helps to set the scene and create an atmosphere of fear and danger that the girls are living and growing up in:
Suddenly, the dark fills with spies who are pad to hear things and report them down at Security... Words repeated, distorted, words recreated by those who might bear them a grudge, words stitched to words until they are the winding sheet the family will be buried in when their bodies are found dumped in a ditch, their tongues cut off for speaking too much.
Note here the metaphor that is created as the words are compared to the "winding sheet" that is pieced together and sewn maliciously by their enemies to create the sheet that will bury them. The emphasis on this process of repetition, distortion and recreation helps create an atmosphere of tremendous fear and danger, as one false word can have incredibly dangerous consequences and end up with your death - or worse.
This quote therefore helps set the scene for the rest of the novel - the butterflies grow up in a world inhabited by danger, fear and caution, where one careless word could be your last.