Gourt Home::Gourt :: Drone (bee)
Drones are male honeybees. Male honeybees develop when the queen bee lays unfertilized eggs.
Drone genetics
It is not clearly understood what prompts a honeybee queen to lay an unfertilized egg versus a fertilized egg. Honeybee eggs hatch regardless of whether they are fertilized. Drones develop only from unfertilized eggs. Unfertilized eggs are haploid in origin, which means that they contain only 16 chromosomes from their mother. The queen and the drones she lays, therefore share a very similar genetic makeup. This type of reproduction is called parthenogenesis.
All chromosomes contain hereditary units called genes. The specific place on a chromosome where particular genes are found is called a locus. All the forms of a gene that might occur at a locus are called alleles. Drones can carry only one type of allele because they are haploid; thus, they are called hemizygous.
Variety in bees is increased when a queen produces an egg. During this time, pairs of chromosomes in cells that are destined to become eggs exchange segments. In this process (meiosis), the chromosome number of germinal eggs is halved. This process results in a haploid egg, with chromosomes having a new combination of alleles at the various loci.
There is much debate in the scientific literature about the dynamics and apparent benefit of the combined forms of reproduction in honeybees. The drones have two reproductive functions. They convert and extend the queen's single unfertilized egg into about 10 million genetically identical male sperms cells. Secondly, they serve as a vehicle to mate with a new queen to fertilize her eggs. Female worker bees, develop from fertilized eggs and are diploid in origin, which means that the sperm from a father provides a second set of 16 chromosomes for a total of 32 - one set from each parent. Since all the sperm produced by a drone are genetically identical, sisters that are more closely related than full sisters of other animals.
A laying worker bee will exclusively produce unfertilized eggs, which develop into drones. As an exception, laying worker bees in some sub-species of honeybees may also produce diploid (and therefore female) fertile offspring in a process called thelytoky.
In honeybees, the genetics of off-spring can best be controlled by artificially inseminating the queen.
Source:
- Breeding and Genetics of Honey Bees John R. Harbo and Thomas E. Rinderer, USDA
Anatomy
Drones are characterized by eyes that are twice the size of those of worker bees and queens, and a body size greater than that of worker bees, though usually smaller than the queen bee. Their abdomen is stouter than the abdomen of workers or queen. Although heavy bodied, drones have to be able to fly fast enough to catch up with the queen in flight.
Drones are stingless.
Development
| Type | Egg | Larva | Cell capped | Pupa | Developmental Period | Start of Fertility | Size | Hatching Weight |
|---|---|---|---|---|---|---|---|---|
| Drone | 3 days | 6 1/2 days | 10 days | 14 1/2 days | 24 days | approx. 38 days | 15-17 mm | nearly 200 mg |
Role
Their main function in the hive is to be ready to fertilize a receptive queen. Mating occurs in flight, which accounts for the need of the drones for better vision, which is provided by their big eyes. Should a drone succeed in mating it will soon die because the reproductive organ and associated abdominal tissues are ripped from the drone's body as copulation occurs. Several drones mate with a virgin queen on her mating flights. Honeybee queen breeders may breed drones to be used for artificial insemination or open mating. A queen mating yard must have many drones to be successful.
In areas with severe winters, all drones are driven out of the hive. A colony begins to rear drones in spring and drone population reaches its peak coinciding with swarm season. The life expectancy of a drone is about 90 days.
Behavior
Drones never exhibit typical worker bee behaviors such as nectar and pollen gathering, nursing, or hive construction. Since the worker bee's stinger is a modified ovipositor (an egg laying organ), the drone is defenceless and can not defend the hive. This has led the drone to be considered as a canonical example of a worthless member of a society. Although the drone is highly specialized to one function, mating and continuing the propagation of the hive, it is not completely without side benefit to the hive. All bees, when they sense the hive's temperature deviating from proper limits, either generate heat by shivering, or exhaust heat by moving air with their wings — behaviors which drones do share with worker bees.
Drones fly in abundance in the early afternoon and are known to congregate in drone congregation areas a good distance away from the hive.
Drones and Varroa destructor
Varroa destructor, the parasitic mite, propagates within the brood cell of bees. The varroa mite prefers drone brood as it guarantees a longer development period which is important for its own propagation success. The number of varroa mites can be kept in check by removing the capped drone brood and either freezing the brood comb or heating it.
References
See also
Entomology | Bees | Beekeeping | Biological reproduction
Drohn | Abeja zángano | Dar | Drönare | 雄蜂
"Drone (bee)"