The Butterflies in Question
The butterflies in the poem "Blue Angels" are Karner Blues, rare, tiny butterflies found in several counties in the state of Michigan as well as in a couple of places in Indiana and Ohio. The butterflies eat almost exclusively from the nectar of the lupine flower and also lay their eggs on the lupine plant. Karner Blues have the same basic color scheme as the Navy's Blue Angels precision flying team.
As may--or may not--be apparent, the italicized lines in the fifth stanza are from Paradise Lost.