Drones are male
honey beeHoney bees are a subset of bees, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s. Drones develop from eggs that have not been fertilized.
Drone Genetics
Drones carry only one type of
alleleAn allele is one of a series of different forms of a gene. The word is a short form of allelomorph , which was used in the early days of genetics to describe variant forms of a gene detected as different phenotypes...
because they are haploid (containing only one set of chromosomes from the mother); thus, they are also called hemizygous. During the queen's egg developing process, a diploid cell with 32 chromosomes divides to generate haploid cells called gametes with 16 chromosomes. The result is a haploid egg, with chromosomes having a new combination of alleles at the various loci. This process is also called arrhenotokous parthenogenesis or simply
arrhenotokyArrhenotoky or arrhenotokous parthenogenesis is a form of parthenogenesis in which unfertilized eggs develop into haploid males.This form is observed in some marine invertebrates, beetles, scorpions, mites, bees, etc....
.
There is much debate in the scientific literature about the dynamics and apparent benefit of the combined forms of reproduction in honey bees and other social insects. The drones have two reproductive functions. They convert and extend the queen's single unfertilized egg into about 10 million genetically identical male sperm cells. Secondly, they serve as a vehicle to mate with a new queen to fertilize her eggs. Female
worker beeA Worker bee is any female eusocial bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen, as well...
s 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 cellA sperm, from the ancient Greek word σπέρμα and and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.Sperm cells contribute...
s produced by a particular drone are genetically identical, sisters are more closely related than full sisters of other animals where the sperm is not genetically identical.
A
laying worker beeA laying worker bee is a worker bee that lays unfertilized eggs usually in the absence of a queen bee. Only drones develop from the eggs of laying worker bees...
will exclusively produce unfertilized eggs, which develop into drones. As an exception to this rule, laying worker bees in some sub-species of honey bees may also produce diploid (and therefore female) fertile offspring in a process called
thelytokyThelytoky comes from the Greek thely, meaning "female", and tok, meaning "birth". Thelytokous parthenogenesis is a type of parthenogenesis in which females are produced from unfertilized eggs. It is rare in the animal kingdom and has only been reported in about 1500 species. It is more common in...
. In thelytoky the second set of chromosomes comes not from sperm, but from one of the three
polar bodiesA polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. It is also known as a polar cell.Asymmetrical cell division leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated into either the...
during anaphase II of meiosis.
In honey bees, the genetics of offspring can best be controlled by artificially inseminating a queen with drones collected from a single hive, where the drones' mother is known. In the natural mating process, a queen mates with multiple drones, which may not come from the same hive. Therefore, in the natural mating process, batches of female offspring will have fathers of different genetic origin.
Source:
- Harbo, John R.; Rinderer, Thomas E. Breeding and Genetics of Honey Bees USDA
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
Mar 1993
- Page, Robert E. Jr.; Gadaub, Jürgen; Beye, Martin The Emergence of Hymenopteran Genetics Genetics
Genetics is a monthly scientific journal publishing investigations bearing on heredity, genetics, biochemistry and molecular biology. Genetics is published by the Genetics Society of America...
, Vol. 160, 375-379, Feb 2002
Anatomy
Drones are characterized by eyes that are twice the size of those of
worker beeA Worker bee is any female eusocial bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen, as well...
s and queens, and a body size greater than that of worker bees, though usually smaller than the
queen beeThe term queen bee is typically used to refer to an adult, mated female that lives in a honey bee colony or hive; she is usually the mother of all the bees in the hive. The queens are developed from larvae selected by worker bees and specially fed in order to become sexually mature...
. 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 |
Drones will die off in late fall and do not reappear in the bee hive until late spring.
Role
The drones' main function is to be ready to fertilize a receptive queen. Drones in a hive do not usually mate with a virgin queen of the same hive because they drift from hive to hive. Mating generally takes place in or near drone congregation areas. It is poorly understood how these areas are selected, but they do exist. When a drone mates with its sister, the resultant queen will have a spotty brood pattern (numerous empty cells on a brood frame); again it is not clearly understood whether this is from higher mortality of the larvae, or by removal of these larvae by nurse bees.
Several drones mate with a non-virgin queen on her mating flights a very small distance away from the hive where she lies in a mating position in front of hive. Mating occurs in flight, which accounts for the need of the drones for better vision, which is provided by their large eyes. Should a drone succeed in mating it will soon die because the penis and associated abdominal tissues are ripped from the drone's body at sexual intercourse.
Honey bee queen breeders may breed drones to be used for
artificial inseminationArtificial insemination is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse...
or open mating. A queen
mating yardA Mating Yard is a term for an apiary which consists primarily of queen mating nucs and hives which raise drones.A Queen bee must mate in order to lay fertilized eggs, which develop into workers.A Mating Yard allows dozens of queens to mate and begin to lay....
must have many drones to be successful.
In areas with severe winters, all drones are driven out of the hive in the autumn. A colony begins to rear drones in spring and drone population reaches its peak coinciding with the swarm season in late spring and early summer. 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
ovipositorThe ovipositor is an organ used by some animals for oviposition, i.e. the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
(an egg laying organ), the drones are defenseless and cannot defend the hive- although if picked up will sometimes try to frighten the disturber by swinging its tail towards the fingers. 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. They will also, in some species, if the nest is disturbed, buzz around the intruder in an attempt to tail.
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 destructorVarroa destructor is an external parasitic mite that attacks honey bees Apis cerana and Apis mellifera. The disease caused by the mites is called varroatosis....
, the parasitic
miteMites, along with ticks, belong to the subclass Acarina and the class Arachnida. Mites are among the most diverse and successful of all the invertebrate groups. They have exploited an incredible array of habitats, and because of their small size most go totally unnoticed...
, 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 combThe brood comb is the beeswax structure of cells where the queen bee lays eggs. It is the part of the beehive where a new brood is raised by the colony...
or heating it.