AbstractFurther experiments were done in an attempt to ascertain the significance of the mandibular glands of nurse bees in female caste differentiation. Groups of 200, 10-day-old nurse bees, with their mandibular glands removed, fed female larvae for 80 h in plastic queen cell cups in the laboratory. After this, each larva finished feeding in a 4-day-old queen cell containing "royal jelly"; final development occurred in an artificial pupation dish. Because four adults, classified as "queenlike intermediates," were reared it appears that (1) mandibular gland secretion is less important as a larval food than that of the hypopharyngeal glands, and (2) if a "queen determining substance" exists the mandibular glands are not its only source.