The drone bee explained

What a drone is

A drone develops from an unfertilised egg and is therefore haploid, carrying only his mother's genetic material. He has a grandfather but no father, and every sperm he produces is genetically identical.

He is bulkier than a worker, with enormous compound eyes that meet on top of his head — around 8,000 facets against a worker's 6,900 — and no sting, no wax glands and no pollen baskets. His mouthparts are too short to feed efficiently from flowers and he is fed by workers for much of his life.

The mating flight

Drones fly out on warm afternoons to drone congregation areas: specific aerial locations, usually ten to forty metres up, which are used year after year and whose position no one has fully explained. Thousands of drones from many colonies gather there and wait for a queen.

A queen flying through the area is pursued in a comet of drones. The successful ones mate in flight; the act ruptures the drone's endophallus, which is torn from his body, and he falls and dies. Between ten and twenty drones mate with each queen, and every one of them dies doing it.

The autumn eviction

As the season closes and forage ends, workers stop feeding the drones, harass them and drag them out of the hive. Evicted drones cannot feed themselves and die within days. A colony going into winter with drones is usually queenless and in trouble.

It is a harsh scene and it is straightforward economics. Drones consume stores and contribute nothing over winter, and the colony's survival depends on those stores.

Are drones useless?

The popular characterisation is that drones do nothing. That is unfair on two counts.

• They are the colony's only route to passing on genes through the male line. A colony that rears no drones has half a reproductive strategy.
• There is evidence that drones contribute to hive thermoregulation simply by being present and generating heat, though this is a side effect rather than a role.
• Their reproductive investment is real: a colony rears hundreds or thousands of drones, at substantial cost, for a small chance that a few will mate.

What is true is that they do no work in the ordinary sense — no foraging, no nursing, no building, no guarding. The word drone entered English as an insult on the strength of that observation, some centuries before anyone understood what they were for.

Drones and varroa

Drone brood is capped for 14.5 days against a worker's 12, and varroa mites reproduce inside capped cells. Those extra days allow substantially more mites to mature, which is why varroa strongly prefers drone brood.

Beekeepers exploit this. Deliberately providing a frame of drone comb, letting it be capped and then removing and destroying it, takes a large share of the mite population with it. It is one of the few varroa controls that involves no chemicals at all.