The themes of "Wintering" by Sylvia Plath are renewal and regeneration and feminine identity and motherhood, all of which have personal meaning for Plath, who writes in self-analysis.
The poet likens her condition to that of winter in which the trees and flora rest and gather their energy to renew themselves. She also compares herself to the bees which form a ball together against the winter's snow. As the speaker enters the cellar, she looks deeply into her soul where she has not done so before:
This is the room I have never been in
This is the room I could never breathe in.
The black bunched in there like a bat,
Black asininity. Decay.
Confronting for the first time the darkness of the recesses of her being, the speaker also feels the strains put upon her by virtue of motherhood:
It is they who own me.
Neither cruel nor indifferent,
the speaker knows that she will survive ("But the torch") as do the bees, who "are all women...The have got rid of the men." These bees/women hold tightly onto one another and ball into a mass that protects them and the hive. "The bees are flying. They taste the spring."
The bees make it to another spring, and they are out of the hive and thriving. Likewise, the speaker has retained her identity and is "flying" in her poetry. The confrontation with her issues and the dark "asininity" help her confront and deal with her identity.