Hypopharyngeal gland (HG) sizes of nurse workers fed or deprived of pollen. HG size was significantly affected by both diet and age in developing workers fed a diet of pollen and honey (grey bars) or a diet of honey alone (white bars), as measured by HG acinus size (mm2). Error bars represent standard error for the mean acinus size across the three colonies (N = 3) tested. Asterisks represent the results of a post-hoc Tukey-Kramer test on the mean acinus sizes for each diet by treatment combination and represent either a p < 0.05 (*) or p < 0.001 (**) level of significance. There was no significant difference in mean acinus size between 3d and 8d old bees fed only honey.