Drones – Bee Males

Information about all the traits of bees, as well as any other species on Earth, is carried by genes, or more precisely, their entire set contained in chromosomes. This set is like a collection of programs building an organism, with most genes indirectly interacting by turning each other on or off at appropriate times. The vast majority of sexually reproducing organisms have two sets of identical genes. One set comes from the father and the other from the mother. If one gene from the pair is damaged but the other from the other parent functions correctly, it usually does not lead to serious consequences. Often, certain genes from one parent are stronger and suppress the activation of the gene from the other parent. In short, this is how it works for the majority of the living world. Genetically, we inherit 50% of our genes from our mother and 50% from our father. Which part of the paternal and maternal pair we inherit is random, hence we share on average 25% of our genes with our grandparents. Siblings on average share 50% of their genes, although it can theoretically range from 0% to 100%.

In hymenoptera, including bees, the situation is slightly different. Drones, or male bees, develop from unfertilized eggs and have only one set of genes, unlike other bees which have two. Therefore, they are 50% related to their mother, the queen, as they receive half of her randomly selected genes. Drones do not have fathers. Worker bees, by probability of gene allocation, are related to drones from 50% to 0%, averaging only 25%. Worker bees are theoretically 75% related to each other because their father has only one set of genes which is always present in the fertilized egg from which they hatch. However, because the queen mates with up to 15 drones during her mating flight, the degree of relatedness among workers varies. This is why we see bees with different exoskeleton colors and temperaments within the same hive, often due to the genetic mix from different breeds or lines.

Mating flights…

Theoretically, bees could reproduce through inbreeding – young drones developing in the hive could mate with young emerging queens. However, the bee genome is full of so-called “stop signs.” This means that when two identical genes appear in critical genome locations, called hot spots, a diploid (having two sets of genes) drone is born from the fertilized egg instead of a worker. This usually results in the family’s extinction or the production of drones in proportions of 25%, 50%, 75%, or 100%. Families with such queens die out because the replacement rate of aging workers is insufficient, and the family’s strength cannot guarantee survival through the winter.

Bees avoid this threat by sending young queens and drones on a so-called mating flight. The young queen flies several kilometers to places where drones from many hives gather, called drone congregation areas. This greatly reduces the likelihood of meeting her own brothers, thus maintaining genetic diversity and the health of the bees.

For several decades, humans have improved methods of bee selection using artificial insemination. This process involves injecting semen from carefully selected drones into a queen anesthetized with carbon dioxide. This has led to significant breeding advances and the development of very valuable and gentle bee lines. However, this approach has drawbacks. Inbreeding and close breeding often activate the stop regions of the bee genome. Additionally, the decrease in genetic diversity leads to an increase in susceptibility to other diseases.

Hopefully, beekeepers will learn to care for genetic diversity and not be driven by short-sighted profit motives and prejudices. They should intensify their efforts and start breeding unrelated lines to maintain diversity.

The Only Males in the Hive

Drones develop from unfertilized eggs laid by the queen bee, but sometimes also by worker bees during her prolonged absence. Drones raised in unsuitable conditions are small, with reduced fertility or are infertile. The development of a drone from egg to maturity takes 25 days, plus about 10 days for the drone to become ready for mating flights. Drones cannot feed themselves; they receive food directly from worker bees. They are raised mainly in late spring and summer. They are quite large, and if numerous, they block the spaces between combs, irritating the bees and causing suffocation. After mating, drones die within a few hours. They do not have a sting; their sole purpose is to provide semen to the spermatheca of future queens. In autumn, drones are expelled en masse from the bee family. Only colonies with a sick queen or no queen at all allow drones to overwinter. They are not adapted to this and usually die entirely during the winter, even if they remain in the hive.