Changing role is a fact of life. As youngsters we are cared for, and as we age we become the carers. And it's similar in bee society. Recently matured young adults take on nursing roles while older bees forage for the nest. But it wasn't clear how a bee's role and age might affect its flight performance. Curious to find out how well nurse bees and foragers hover as they age,Stephen Roberts and his colleagues from the University of Nevada decided to investigate the flight capacity of hovering bees to see how their performances change as they switch from nursing to foraging(p. 2604).

Collecting nurse bees and foragers that hatched at the same time, the team weighed the insects, filmed them hovering in air and thin heliox, and found that the foragers were 42% lighter than nurse bees of the same age. But instead of losing muscle, the foragers had lost weight from their abdomens,effectively increasing their proportion of flight muscle. But would this make the foragers better fliers?

Analysing the insect's flight performances, the team found that the nurse bees were unable to hover in the thin heliox. Even in normal air, the heavier nurses were only just able to support their weight: they were already beating their wings as fast as possible just to stay aloft in normal air. And when the team compared old and young nurses, they all hovered equally `well'.

However, the lighter foragers had no difficulty hovering in normal air, and could beat their wings 32% faster than in air in order to remain airborne in heliox. Comparing young and old foragers, it was clear that the youngest foragers could not beat their wings as fast as middle-aged foragers at the peak of their performance. So the foragers' hovering performance altered as they aged.

What does this mean for the occupants of a bees' nest? Roberts and his colleagues explain that bees are versatile creatures and can switch roles in response to environmental conditions. But young and old foragers, with lower flight capacities than middle-aged foragers, may not be able to keep the nest as well stocked as their middle-aged sisters, and nests that tend to produce very young foragers could be at a disadvantage compared with nests whose nurses graduate to foraging later in life.

References

Vance, J. T., Williams, J. B., Elekonich, M. M. and Roberts, S. P. (
2009
). The effects of age and behavioral development on honey bee (Apis mellifera) flight performance.
J. Exp. Biol.
212
,
2604
-2611.