In chapter 7 the quote relates to bees and sexuality:
How did bees ever become equated with sex? They do not live a riotous sex life themselves. A hive suggests cloister more than bordello.
(—The Queen Must Die: And Other Affairs of Bees and Men)
The quote is referencing the idea of the “birds and the bees,” when people have to give a sex talk, and they reference birds and bees as a metaphor for nature and reproduction. Bees are not sexual beings though, instead, they are industrious—going about their work. The incorrect association of bees with sexual reproduction is tied to the idea of bees being active during Spring, which is a metaphor for the creation of new life. However, the novel is using this quote to clarify its own metaphor about bees.
Specifically, the novel uses bees as a metaphor for women. The queen bee leads just as August Boatwright leads her household and business. The Boatwright house is full of women, but unlike the stereotype of a brothel (the typical house that would be full of women), the women of the Boatwright house are focused on their relationships with one another and the labor of their hands. The Boatwrights have a very productive honey farm, and their experience is more like a cloister with a focus on work and relationships.
The movement away from men is a healing action in the novel. Just as Lily gets away from her father and learns about womanhood through the devotion to the Black Madonna and life at the Boatwright house—the Boatwrights themselves tend to eschew standard social norms in relation to courtship and marriage. The metaphor for bees, therefore, holds up well for describing life in pursuit of industry rather than what was normal for women at the time—a life serving as both a wife and mother, which is intrinsically tied to sex.