Average HPG acinus diameter (μm) in: (A) bees after 24 h of treatment; (B) bees after 48 h of treatment; and (C) bees after 72 h of treatment with coumaphos or imidacloprid. Bees were divided into four age groups: first (1–6 days); second (7–12 days); third (13–18 days) and fourth age group (18–32 days). Sample sizes are n = 10 − 30; Same letters indicate that Scheffe tests (P < 0.05) established that HPG diameters after imidacloprid or coumaphos treatments of 24, 48 and 72 hours duration were not significantly different.