Collective and individual nursing investment in the queen and in young and old honeybee larvae during foraging and non-foraging periods

Summary.

Unsealed honeybee larvae and the honeybee queen strongly depend on a rich supply of proteins. Worker bees feed both the queen and the larvae with proteinaceous secretions derived from pollen. We interrupted the bees' pollen income by simulating a period of rain (non-foraging) and observed the effects on the care of young and old larvae and on the behavior of the queen. Although the queen's general activity level decreased during non-foraging periods, neither the number of her trophallactic contacts nor her egg laying rate was significantly affected. In contrast, the impact on the nursing of young (two-day-old) larvae was severe: nursing periods diminished to 16% of the initial level. The negative effects persisted until the fourth day after the artificial rain ended. For older (five-day-old) larvae, nursing periods were reduced only until the third day, after which they increased again, even though the non-foraging conditions continued. The number of larvae in the colony also changed with the weather conditions. In conclusion, faced with prolonged non-foraging conditions, the colony responds with two age-dependent resource saving strategies: (1) nursing of young larvae declines and (2) with older larvae the workers reduce the nursing efforts for a few days, then, as the larval population declines through cannibalism, the nursing periods granted to the surviving old larvae increase and nurses favor the older larvae. Older larvae represent a greater investment of resources and are closer to the final capping stage, when they no longer require feeding.