"With its frail kites of furious butterflies" Alliteration of the 'f' sound. The butterflies are frail/delicate
"Black maid shaking linen as she sings, the plain notes of some protestant hosnanna" Black slaves would sing hosannas to God. (symbolic to slavery)
The poem is symbolic to the suffering of nature and how mankind can be cruel and takes apart in causing the destruction and harm onto nature . And how Cruelty can start from a young age
"The little surgeon pierces the thin eyes. Crouched on plump haunches, a mantis preys" Metaphor. Compares the little girl to a surgeon and a mantis, which further emphasizes on the tortures being enacted to the butterfly.
"Heredity of cruelty everywhere"- symbolic to how normalized cruelty has become as it passes from generation to generation. And how it affects both nature and mankind.