Updated: Mar 2
Not as glamorous as the queen or as famous as the worker bee, drones aren't around for long but they have a very important job
It's the end of summer and the colony is gearing up for winter - workers are gathering the last ivy nectar and doing a little tidying up. This includes male honeybees (drones). The workers are pushing them out of the hive and refusing to let them back in. Sadly, they'll die within a few days.
But what was their purpose in the hive and why aren't they wanted now? Sex (or more accurately, reproduction) is the key!
The honeybee colony is a sisterhood - of female worker bees and their queen. At its peak, in early summer, there may be perhaps 60,000 bees. The vast majority of these will be workers and there will be one queen. The queen is the life-force of the hive and she grows the colony by laying about 2,000 eggs a day. If things go right, the colony reaches a point where there are lots of bees and honey but no more space - the colony is ready to reproduce. The colony does this by swarming - a process in which the queen plus about half the workers leave the hive to fly to a new nest site. They leave behind a new queen and the other half of the workers in the old hive. So one colony becomes two.
Looking with human eyes, the drone's lifecycle is fascinating and perhaps rather shocking. From the honeybee's point of view, it' is an evolutionary masterstroke
To be able to swarm in the first place though, the colony needs to produce a new egg laying queen - a replacement for the old queen who will soon fly away. The hive does this by feeding a female larva with super-rich food. This high-calorie, high-protein diet develops an adult queen in about 2 weeks. A few days after she has emerged, the young queen will leave her hive and look for a mate on the wing.
This is where drones come in! As well as making queens, the colony has been rearing males - about 1,000 to 5,000. But these males aren't destined to mate with their own hive's new queen - like pollen on the wind, they will fly out of their hive searching for a new queen from another hive. This is a drone's one and only purpose - to carry his colony's genes out into the world by mating with a queen.
Each day, the drones fly out. Typically, they fly to a drone congregation area - an area of open sky where thousands of other drones from other colonies gather. They wait for young un-mated queens to arrive. These areas can be up to 7kms from their own hive but how the drones and queens identify these areas and know to fly to them, no-one really knows. When a young queen does arrive, she is spotted by the drones. Those that see her will fly to catch up with her - the first one to catch her, will mate with her. Having mated, the successful drone will fall to the ground - dead.
Drones are built for their task. Firstly, a successful drone needs to be able to fly long distances and to fly faster than any other to catch the queen. Secondly, a successful drone needs to be able to spot a queen from a distance. So, drones have big chests with big flight muscles. They also have huge compound eyes. The video shows drones at the entrance to a hive (they are the big furry bees off to the left) and the picture below shows their massive eyes in more detail. As a comparison - a queen doesn't do much flying so she has 4,000 cells in each eye, a worker has 6,900 cells and the drone's big eyes have 8,600.
Chasing and mating continues until the queen has mated with 15-20 other drones. If she has mated with enough drones, this will be the only mating flight she makes. She will keep the sperm fresh in her sperm gland over the several years of her life - enough to fertilise about 200,000 eggs a year.
So, what we have is a big game of genetic roulette.
Because of the distance from her hive and the large number of congregating drones, it's unlikely that a new queen will mate with any of her "brothers" i.e. outbreeding rather than inbreeding. Even more importantly, the queen will populate the hive with worker bees that have one of many different fathers. Each group of half-sisters can have different characteristics - some might be great at finding water whilst other's may be particularly good at remembering sources of nectar, say. Get a winning combination of all these potential attributes and your hive will be successful enough to survive the winter and to swarm next year. When it comes to raising new queens in the spring, they will have different fathers too - potentially bringing new and different features to the colony.
But what about the unsuccessful drones? They fly to the mating grounds each day or they hang round a hive on the look out for a new queen. A clever interplay of pheromones means that they ignore a sister queen in their own hive (again avoiding inbreeding). Having no sting, they are not a threat to a colony and so the workers will let in drones from other hives. Whilst waiting to fly out each morning, the drones just hang around; doing no work and being fed by the workers. And here is the reason for their rather sad end.
As autumn approaches, the colony has no need of drones. The hive will need all its resources to survive the winter. The workers stop feeding them and shove them out into the cold. Rather harsh for the drones but for the sisterhood, it makes perfect sense.
Just so you know - this amazing close up of a drone comes from Gilles San Martin via https://creativecommons.org/licenses/by-sa/2.0/