Bees leaving loaded with honey from an observation hive entrance pipe. The arrows point out the robber bees. The robber bees enter and leave the hive with little or no harassment by the colony’s bees. Engorged full of honey, their swollen abdomens droop down while in flight. I use that “abdominal droop” to spot the robber bees leaving the hive. I use a similar abdominal droop to spot a flying queen.