In the semiological theory of Saussure and Barthes, a first-order level of signs (the level of assigned meanings, or denotation) is augmented by a second-order level (of associations, or connotations). Behind the apparent meaning is an ideologically-motivated set of cultural assumptions on which the meaning draws.
But connotations are notoriously vague. They are as likely to lead, in reverie, to the dissolution or diversion of meanings as to their condensation. Poetry seems to be an art that hesitates and hovers, keeping the uncertainty of connotations in play for as long as possible.
These days, no one knows the names of butterflies, so for a brief moment the words of the names can float free from any indicative function, their colours released.