Drone-laying colonies that requeen

(by Janine Kievits)

A drone-laying colony normally has no future. It can raise only males, either because its queen has lost the ability to fertilise the eggs she lays, or because there is no queen at all and laying workers have taken over. And yet, from time to time—very rarely, but it does happen—a beekeeper is surprised to discover a fine brood developing in a hive whose frames he was about to shake out. How can this be possible?

Drone-laying colonies and thelytoky – when workers produce queens again

A drone-laying colony is usually considered doomed: without a fertile queen, worker bees lay unfertilized eggs that develop only into drones. This article shows, however, that in rare cases workers can produce female offspring—and even new queens—through a process known as thelytokous parthenogenesis.

In honey bees, normal reproduction follows arrhenotokous parthenogenesis: unfertilized eggs develop into haploid males, while fertilized eggs produce diploid females. Thelytoky is an exceptional form of parthenogenesis in which diploid females arise from unfertilized eggs. At the cellular level, this occurs through fusion of the egg nucleus with a polar body, which functionally replaces fertilization.

Although parthenogenesis is common in many animal groups, thelytoky is rare in honey bees. A notable exception is the Cape honey bee (Apis mellifera capensis), whose workers routinely produce female offspring, including queens, via thelytoky. This confers a strong evolutionary advantage but becomes highly problematic when Cape bees parasitize colonies of other subspecies, often leading to colony collapse.

In European honey bees, thelytoky is possible but extremely uncommon. Historical experiments and selective breeding trials show that certain genetic lineages can occasionally produce female offspring from laying workers, but success rates are typically below 1 % and vary widely between lines.

Thelytoky may act as a short-term rescue mechanism in queenless colonies, but it cannot replace sexual reproduction. The lack of genetic recombination reduces long-term adaptability and evolutionary potential.

In summary, drone-laying colonies are not always biologically hopeless, but the production of queens via thelytokous parthenogenesis remains a rare and exceptional phenomenon with no practical relevance for routine beekeeping.
 

See also:

• The drone-laying colony
• Drones: The Indispensable Luxury
• No Sex, No Problem
• Introduction to Bee Genetics
• All About the Drone
• Apis mellifera and Other Apis

Article published in: La Santé de l’Abeille, No. 281, pp. 403–412, October 2017