Colony queen number, a major feature of social organization, is associated with worker genotype for Gp-9. Colonies are headed by either a single reproductive queen (monogyne form) or multiple queens (polygyne form). Differences in worker Gp-9 genotypes between social forms may cause differences in workers' abilities to recognize queens and regulate their numbers (By similarity). Homodimer. Belongs to the PBP/GOBP family.