The life & death of a Drone
Honeybee colonies contain the following three distinct castes of bee: A single queen bee, female worker bees and male drone bees.
The three castes of Apis Mellifera
Genetics of a drone.
A drone is a male bee and is larger than a worker bee but not as long as a queen bee. He also has much larger eyes than a worker bee and queen bee.
Drones are haploid meaning they are fatherless as they hatch from an unfertilised egg. They do however have a grandfather as its mother (the queen) hatched from a fertilised egg. They contain only 16 chromosomes unlike the queen and worker bees who being female contain a full set of 32 chromosomes.
Why are drones needed in a colony?
Drones are considered by many beekeepers as lazy as unlike female worker bees the drones do not clean the hive, collect nectar, pollen, water or propolis, build honeycomb, feed larvae, cap brood cells, feed the queen or sting intruders. Unlike a queen or worker bee a drone cannot sting as it does not have a stinger.
They are also unable to feed themselves and need worker bees to assist them with this.
Their main purpose is to mate with virgin queens from another honeybee colony and in doing so they increase the gene pool by spreading their genetics to ensure the continued survival of honeybees.
Drones perform precisely the role that nature gave them, and as such, they are a vital part of the honey bee colony. Kovac et al (2010)
Their larger size can also benefit the hive as it allows them to help worker bees control the temperate inside the hive & generate more heat by vibrating their larger wings.
Drone congregation areas.
When drones reach sexual maturity at two weeks old they leave the hive in the afternoon to fly to drone congregation areas. Drone congregation areas are locations where drones from up to 200 different colonies group together at heights of 10 to 40 metres in the air where they wait for a virgin queen to enter and then attempt to mate with her. How drones find these drone congregation areas is still not fully understood but it is believed that magnetite in their abdomen allows them to navigate there using the Earths magnetic field.
Only 1 in 1000 drones succeed in getting a chance to mate with a virgin queen.
Drones can fly at up to 22mph when trying to mate with a queen.
Worker bees decide when drones are needed.
Worker bees decide on when and how many Drones are needed. They make special sized drone brood Cells which are larger than worker bee brood cells. When the queen is laying an egg she reverses up to an empty brood cell and uses her long hind legs to measure if it's a worker or drone cell. If it's a worker sized cell she will mix her stored sperm with the egg as it's being deposited in the cell. However if she feels a drone sized cell she will deposit an unfertilised egg in the cell.
Death of a drone
Drones can live anywhere from 30 days to 90 days. If they successfully mate with a virgin queen the force of the sperm being ejected into the queen will tear the drones endophallus from his body (leaving it lodged in the queen) and the drone will fall to the ground where he will die within minutes.
Drones don't overwinter in the hive as they would eat too much of the colonies stored honey and so threaten the survival of the colony. So in Autumn the worker bees forcibly eject all of the remaining drones from the colony where they die in the low temperatures outside the hive. If the colony survives the winter then new drone eggs will be laid and hatched and the life cycle of drone honeybees will repeat again.
This photograph shows a drone bee that was forcibly removed from one of our colonies of honeybees. The worker bees stand guard at the entrance to the hive to prevent him from returning. This drone then succumbed to the cold temperatures outside.
References
Stabentheiner A, Kovac H, Brodschneider R (2010) Honeybee Colony Thermoregulation – Regulatory Mechanisms and Contribution of Individuals in Dependence on Age, Location and Thermal Stress. PLoS ONE5(1): e8967. https://doi.org/10.1371/journal.pone.0008967