Thursday, 8 December 2011

The Drones

The Drones were a mancunian punk band in the late seventies. In 1977 they released a 7" bearing the songs Bone Idol and I Just Wanna Be Myself. In the 80's a mate of mine bought a second hand copy of this at a market someplace and I still have a recording of it on a C90 somewhere, unfortunately I don't own a cassette player anymore so it's unlikely I'll be listening to them in the near future. They knocked out two studio albums and appeared on a couple of compilations before fading into obscurity so you can be forgiven for not having heard of them prior to reading this, shame really as Bone Idol was a pretty decent song and I'd've liked to have heard a bit more from them. Anyway this entry isn't really about them. It's about the other drones, male bees.

Looking at the comb over summer it was easy to spot several larger looking bees ambling about amongst the workers. I'm sure I'm not the first new beekeeper to have spotted a drone and thought it was the queen only to then see another five happily wandering about on the same frame and realise it's not her.

Workers and Drones on new foundation.
The drones are the two larger ones in the picture. Apart from being bigger than the workers they have a wider thorax and the abdomen has a rounded end whereas the worker bees are more pointy and wasplike. Whilst not quite so visible in the image drones have huge eyes extending from the sides of the head right over the top whereas workers have smaller ones on the sides of their heads. The reason for the drones' huge eyes are so that they can spot queen bees on mating flights. As the name suggests they make a very loud noise as they fly -well loud for a bee anyway.

Worker and Drone
The above pair were happy to pose together so we can compare the worker (on the left) and the drone (on the right). You can see the top of the drone's head is covered with it's compound eyes so it appears to be wearing a little bifurcated helmet. Honeybees actually have five eyes, the two large compound eyes that you can easily see and then three very small simple eyes in the middle of the head. The simple eyes seem to measure light levels. You can also see the worker has an abdomen tapering to a pointy end which houses a sting whereas the male has a very rounded end with some fuzzy hair just visible in the image. There's no sting on the drone. You can also make out that the legs are different on the drone to the worker, they're longer on the drone, presumably for hanging onto the Queen during matin.

The role drones play in a bee colony remains something of a mystery. They have some obvious jobs to do but  most of the time they just appear to be a burden on resrouces. Drones don't forage, they don't make wax, they don't draw wax, they don't feed larvae, they don't clean the hive, they don't do door security, it appears that they don't really do a lot -they don't even feed themselves if they can help it! Their most obvious role is mating with queen bees, given the number of queen bees in a normal colony (one) compared to the number of drones (a few hundred) the odds are seriously stacked against any individual drone ever performing this task -which may be just as well as they die with a ruptured abdomen shortly afterwards anyway. They quite probably have other roles that we just don't understand at present. What is known is that bee colonies seem to want to have a contingent of drones in their numbers. It has been suggested that given their larger size and noisy flight they may act as decoys to birds and other predators when a colony swarms. A potential predator seeing a swarm will probably go with the biggest fattest looking bee in the swarm which without the drones would be the queen. So perhaps the drone is a self sacrificing decoy. The loud noise they make could also be to attract predators.

To mate drone bees from different colonies go to congration areas, how they find them is quite a mystery bearing in mind that no drone lives longer than a single season so there's nobody passing the location along to next year's drones. Anyway the guys hang out at these congregation sites waiting for a queen. Eventually a virgin queen will emerge from a colony and fly over to the congregation zone too -maybe she hears the drone's noise? Once there she'll mate with about 17 drones, somehow they avoid mating with any from their own colony -no inbred two headed, three legged bees for us thanks. The reward for drones who have successfully mated with a Queen is a fatal ruptured abdomen, the queen goes back to her colony to spend the rest of her life in the dark laying eggs.

Drones that haven't mated live happily in the hive till it gets a little cooler at which point the worker bees stop feeding them and drive them out into the cold to die of hunger and exposure. Either way it's not a happy ending for the drone.

It's a bit of a mystery how the bees decide how may drones they need but it's something the worker bees seem to dictate rather than the queen. I read somewhere that a typical strong colony has between 400 and 600 drones. As drones are bigger they need slightly larger cells in the honeycomb. When the workers want drones they will make the larger comb if there is room but if there isn't the space they'll tear down some existing comb to make the larger cells. As the queen bee lays her eggs in empty cells she'll normally lay an egg in a worker cell and fertilise it which makes the egg female, when she reaches a  larger drone cell she lays an egg and doesn't bother to to fertilise it leaving it with half a set of chromosomes. Wierd eh? This will then hatch into a drone.

Normally drones make up a small portion of the colony population, however sometimes things go wrong and drone  numbers increase. Sometimes a queen will start laying only or mostly drones -this is called a 'drone laying queen' and can be rectified by removing the queen (squish!) and replacing her with a new one. The other instance when a drone population will increase is when there is no queen and worker bees start laying eggs. Worker bees never get to mate so their eggs are never fertilised which means theirs always hatch into drones. At this stage the colony is pretty much knackered and the normal thing to do is empty the colony on the ground in the hope that non laying workers will find their way into other existing hives to bump up their workforce.

Worker cells above, drone cells below.
As the drones have bigger cells this makes them useful in the fight against the Varroa Destructor mite. The mite's prefer to lay their eggs in drone cells as there's more room ion the cell and a bigger larvae for the mites to feed on. Beekeepers can take advantage of this by encouraging the bees to make drone comb on a specific frame then when the drone larvae in their cells have been capped to begin the metamorphosis into actual bees the keeper can take away the comb and all the mites it contains. This is a technique usually referred to as "Sacrificial Drones" or "Sacrificial Drone Comb" as basically the developing drones are sacrificed to cull the mites.

Whilst the workers will tear out worker cells to make drone comb they can also be directed to make drone cells where the beekeeper can more easily access them. It's very simple to do. The beekeeper places at one end of the brood box a frame of foundation which is only half the height of the brood box. The bees then make their new drone comb hanging from the bottom of this frame.

Drone comb being made underneath a shallow frame.
This means that not only can the beekeeper easily locate the drone comb but it can be easily removed. Once removed it goes into the freezer to kill the larvae and the mites alike so they can later be counted giving the keeper some idea of scale of the the colony's mite problem. Killing them in the freezer is actually far more humane than it sounds. Bees aren't hot blooded like we are, in the evenings stray bees in the garden can be seen to grind to a halt as the temperature drops, if it doesn't drop too low they can be seen moving again in the mornings.

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