Secret of worker layers

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Queen Bee
Nov 8, 2008
Reaction score
Finland, Helsinki
Hive Type

Worker reproduction is low in honey bee (Apis mellifera)
colonies with a queen (1, 2), because a suite of pheromones
derived from the queen and the brood inhibits ovarian
development in workers (3). Moreover, workers with developed
ovaries are attacked by other workers (4). Nevertheless, a
considerable proportion (4%) of workers can have functional
ovaries (5) and can lay a substantial number (7%) of male eggs
(6). Therefore, a crucial factor restricting successful worker
reproduction in honey bees seems to be the removal of workerlaid
eggs by other workers (worker policing) (7). Worker policing
has been the focus of many theoretical and empirical studies in
a wide range of species of social Hymenoptera (7–12). This
behavior is considered adaptive in species in which queens mate
multiply, causing workers to be on average more closely related
to the son’s of the queen than with sons of other workers (8, 9).

It has been postulated that queen honey bees mark their eggs
with a queen-specific pheromonal label, providing the proximate
cue for worker discrimination between queen-laid and workerlaid
eggs (13).

IN most species of social Hymenoptera with queen–worker dimorphism, workers cannot mate but retain functional ovaries1; because males arise from unfertilized haploid eggs, workers can potentially produce males. Worker-derived males are frequent in some species, but in others occur only in queenless colonies2,3. Workers are more related to their own sons (coefficient of 0.5) than to the queen's sons (their brothers; 0.25); they are also more related to nephews (0.375) than brothers if queens mate with one male, but if queens mate with more than two unrelated males a worker's mean rela tedness to nephews is less than to brothers3–5. In this case workers could benefit by 'worker policing'3,5: prevent-ing each other from producing males, perhaps by destroying worker-laid eggs or by aggression toward reproductive workers. Worker reproduction is rare in queenright colonies of species with multiply mated queens (such as honeybees6 and some yellowjacket wasps7), but is common in some monandrous species (bumblebees and stingless bees3). Here we describe experiments showing strong discrimination by honeybee (Apis mellifera) workers against worker-laid male eggs, supporting the worker-policing hypothesis. The honeybee was studied because queens mate with 10–20 males8, making worker policing seem likely as a cause for the rarity of worker-derived males (about one in a thousand males is worker-derived6).


In queenright colonies of Apis mellifera, worker policing normally eliminates worker-laid eggs thereby preventing worker reproduction. However, in queenless colonies that have failed to rear a replacement queen, worker reproduction is normal. Worker policing is switched off, many workers have active ovaries and lay eggs, and the colony rears a last batch of male brood before dying out. Here we report a colony which, when hopelessly queenless, did not stop policing although a high proportion of workers had active ovaries (12.6%) and many eggs were laid. However, all these eggs and also worker-laid eggs transferred from another colony were policed. This unusual pattern was repeated eight weeks later by a second queenless colony made using worker bees from the same mother colony, which strongly suggests genetic determination.
One would have to wonder whether the drones produced under these circumstances are capable of fertilising a queen in a normal DCA. If so there would be a genetic advantage to the laying workers in the doomed hive.

Are they?