In the honeybee, Apis mellifera, vitellogenin (Vg) expression has been detected in the ovary of queens, but not in that of workers. In addition, larvae of both sexes produce Vg in significant amounts, which suggest that Vg serves for functions additional to oocyte growth and energy supply to the embryo. In vivo hormone treatment experiments suggest that the decrease of 20-hydroxyecdysone concentration occurring in previtellogenic phases allows Vg production. Southern analysis indicates that the Vg gene is present as a single copy in the honeybee genome. Arch. Insect Biochem. Physiol. 59:211–218, 2005. © 2005 Wiley-Liss, Inc.