The Drone

The drone (male bee, male honey bee) is the member of the honey bee colony that develops from an unfertilised egg, has no sting and whose only task is to mate. He is easy to recognise in the hive by his large body, his huge eyes meeting on top of the head and his deep buzz. For the beekeeper, the drone is an important indicator of queen quality, varroa pressure and queenlessness.

What is a drone bee and what does he do in the colony?

The drone is the colony's reproductive partner. He takes no part in hive work: he does not collect nectar or pollen, build comb, feed brood or defend the hive. His task is to mate in the air with young queens from other colonies, carrying his mother's genes on to the next generations.

A strong colony supports from a few hundred to a few thousand drones through spring and summer. This is a food burden; the colony takes on this cost only when forage is plentiful. A normal colony has no drones in winter.

• Genetic carrier: The drone passes on the genes of the queen that is his mother. That is why breeders often describe the drone as "his mother's flying germ cell".
• Colony reproduction: A colony spreads its genes not only by swarming but also by fertilising the queens around it through its drones.
• An indicator for the beekeeper: The amount, location and timing of drone brood give information about the colony's strength, swarm preparations and the state of the queen.

How is a drone bee produced?

The drone develops from an unfertilised egg. Before laying, the queen checks the cell with her front legs; she does not fertilise the egg she lays in a wide drone cell. That is why the drone has no father, but does have a grandfather: his mother's father.

Because he comes from an unfertilised egg, the drone carries only one copy of each chromosome. All the sperm he produces are genetically identical. Sister workers fathered by the same drone are therefore very closely related to each other.

Why are drone cells larger?

A drone cell is clearly wider than a worker cell: a worker cell is about 5.2–5.4 mm across, while a drone cell is about 6.2–6.9 mm. The bees mostly build drone cells on the bottom and side edges of the frame and in gaps between combs. The cappings of sealed drone brood are domed like bullet heads.

If you see scattered drone brood with domed cappings in worker cells, there is a problem. It is a sign either of a queen that has run out of sperm (a drone-laying queen) or of laying workers that have started laying in a colony left queenless. Because these drones grow in narrow cells, they are smaller than normal.

How many days does it take for a drone to emerge?

The drone takes the longest of the three castes to develop: about 24 days from egg to adult. The longest part of this is the sealed (pupal) period.

Times can vary by a day or two with temperature and race. The long sealed period explains why varroa prefers drone brood: the longer the mite stays in a sealed cell, the more offspring it raises.

How do you recognise a drone bee?

Recognising a drone in the hive is easy; in the first years, what beginners really confuse are the queen and the drone.

• Eyes: Very large and touching each other on top of the head. In the worker and queen the eyes sit separately on the sides of the head.
• Body: Larger and stockier than a worker, about twice the weight. The tip of the abdomen is blunt and rounded; the queen's abdomen, by contrast, is long and pointed.
• Antennae: They have one extra segment and carry many scent receptors that detect queen pheromone from a distance.
• No sting: The sting is a modified egg-laying organ; males do not have one.
• No working organs: No pollen baskets, wax glands or royal jelly glands; his tongue is short and he cannot take nectar from flowers.
• Sound: He buzzes more deeply and loudly in flight; although this alarms beginners, he is harmless.

How long does a drone bee live?

A drone emerging from his cell is fed by the workers in the first days, then eats honey himself. He reaches sexual maturity in about 10–12 days; meanwhile he makes short orientation flights. In summer his life span is usually a few weeks. A drone that mates dies immediately; those that fail to mate either die of old age or are expelled from the hive at the end of the season.

Drones drift easily from hive to hive within an apiary. They are generally accepted in other colonies too. So not all the drones you see in front of a hive necessarily belong to that hive.

How do drones mate?

Mature drones leave the hive on warm, sunny days, mostly in the afternoon. Drones from many colonies wait tens of metres above the ground in drone congregation areas, which form in roughly the same places every year. When a young queen flies into this area, the drones find her both with their large eyes and by detecting her queen pheromone.

1. Mating happens in the air. The drone grips the queen and his reproductive organ turns inside out (everts) to release his sperm.
2. The drone dies. Part of the organ breaks off and stays in the queen; the drone is paralysed and falls.
3. Mating sign: The whitish piece left at the tip of the queen's abdomen is removed by the next drone or by the workers in the hive.
4. Multiple mating: In one or a few flights the queen usually mates with 10–20 drones and stores the sperm she collects in her spermatheca for life.

Congregation areas may be several kilometres from the hive. That is why the beekeeper cannot fully control which drones a queen will mate with; the drones of all the colonies in the area are involved.

Why do drones matter? Breeding and queen quality

A worker bee gets half of her genes from her father, that is, from a drone. If a high-quality queen mates with drones from bad-tempered or disease-prone colonies, her offspring will not fully carry their mother's superior traits. Multiple mating gives the colony genetic diversity; this diversity strengthens disease resistance and the colony's organisation.

A beekeeper who rears queens should also plan the drone source:

• Selected father colonies: In spring, give drone comb or an empty frame to colonies that are gentle, strongly hygienic, productive and resistant to varroa.
• Reduce unwanted drones: In bad-tempered or weak colonies, limit drone brood with a drone-trap frame.
• Timing: Drones take about five weeks to mature (24 days of development and 10–12 days of maturation); the queen rearing calendar is set up accordingly.
• Healthy drones: Drones from well-fed colonies with a low varroa load are of higher quality; mites and viruses can weaken drones' development and reproductive capacity.

For controlled mating, isolated mating stations or instrumental insemination are used; these are methods that require expertise.

Drone brood and varroa: how to use a drone-trap frame

The Varroa destructor mite chooses drone brood for reproduction several times more often than worker brood. This preference is used to trap part of the mite population.

1. In spring, when the colony has grown strong and starts building drone comb, give the brood box a frame without foundation or a half frame (drone-trap frame).
2. The bees build drone cells in the gap and the queen lays in them.
3. After the drone brood is sealed and before the drones emerge (within the first week after capping), cut out and remove the sealed section of comb.
4. Destroy the cut piece by freezing or melting it; put the frame back.
5. Repeat the procedure for several rounds in spring and early summer.

Opening sealed drone pupae with a fork and looking for mites also gives a quick idea of the varroa level. The method slows mite increase but is not enough on its own; it must be used together with regular mite counts and, when necessary, a licensed treatment.

Why are drones expelled from the hive in autumn?

When the nectar flow ends and winter approaches, the workers stop feeding the drones, push them to the edges of the combs and finally drag them out of the hive. Drones that cannot fly or are left outside soon die. This seemingly harsh behaviour is the colony protecting its winter stores.

On the other hand, if there are still many drones in the hive in late autumn or winter, there may be a problem in the colony: queenlessness, an old or drone-laying queen, or laying workers. In such a colony, check whether there are eggs and young larvae.

• Plenty of drones in spring: Normal; a sign of a strong colony and the approaching swarming season.
• Scattered drone brood in worker cells: A problem with the queen or laying workers.
• Drones not expelled in autumn: Check for queenlessness.