In a honey bee colony, all worker bees are indeed female. This remarkable characteristic is a fundamental aspect of bee social structure, setting the stage for the intricate division of labor within the hive. Understanding why worker bees are exclusively female involves exploring their diverse responsibilities, the roles of other bees in the colony, and the unique biological mechanism governing bee sex determination. This arrangement is central to the colony’s overall function and survival.
Tasks of Female Worker Bees
Female worker bees perform many essential duties throughout their relatively short lives, typically about five to seven weeks. Their initial tasks, as “house bees,” involve cleaning and preparing cells for new eggs, and caring for developing larvae. These young workers feed and groom the brood, ensuring the brood’s health.
As they mature, worker bees take on specialized roles within the hive. They build and repair wax combs, manage the hive’s temperature by fanning their wings, and receive nectar and pollen from foraging bees. Older workers transition to “field bees,” venturing outside the hive to collect resources like nectar, pollen, water, and propolis. Foraging activities provide the colony’s food. Worker bees also act as guards, defending the hive entrance from threats.
Other Bees in the Colony
A honey bee colony also contains two other types of bees: the queen and male drones. The queen is the largest bee in the hive and is the only fertile female. Her role is to lay all the eggs for the colony, which can be up to 2,000 eggs per day during peak season. She also produces pheromones that regulate the behavior of other bees and maintain colony unity.
Male drones are larger than worker bees, do not possess stingers, and do not participate in foraging or hive maintenance. Their function is to mate with a virgin queen from another colony. Drones develop from unfertilized eggs and are a small percentage of the hive’s population. They are expelled from the hive before winter because they consume resources without contributing to the colony’s survival tasks.
The Unique Biology of Bee Sex Determination
All worker bees are female due to haplodiploidy, a biological process governing sex determination in honey bees and other Hymenoptera. In this system, females develop from fertilized eggs and are diploid, meaning they have two sets of chromosomes. Males, or drones, develop from unfertilized eggs and are haploid, possessing only one set of chromosomes.
The queen controls whether an egg is fertilized. When she lays an egg, she can fertilize it with sperm stored from mating flights, resulting in a female offspring. If an egg is laid unfertilized, it will develop into a male drone. This mechanism ensures that all diploid individuals are female.
Haplodiploidy results in unique genetic relatedness among female bees. If a queen mates only once, her daughters (worker bees) share, on average, 75% of their genes with their full sisters, a higher degree of relatedness than the 50% they would share with their own offspring. This increased genetic similarity among sisters contributes to the altruistic behavior observed in worker bees, as helping sisters reproduce passes on a significant portion of their own genes.
The diet a female larva receives also determines her role. Larvae fed royal jelly develop into queens, while those fed honey and pollen become sterile worker bees.