A handful of foragers return home early one morning, their stomachs heavy with nectar. They have found a good source of food, but it will take more honeybees to collect it all.
Inside the hive a worker suddenly charges at a bee, pushing with her head and grabbing with her feet. She jumps on top of the bee and shakes her abdomen up and down. The bee responds to this strange behaviour by walking off to the hive entrance. There she will watch the waggle dances on the propolis dance floor and join the foraging efforts of her sisters.
The worker had demonstrated the dorsoventral abdominal vibrating dance or DVAV, a dance to recruit more bees to forage during a sudden or plentiful flow of nectar.
The DVAV might also be used on a queen bee to make her move towards the entrance when it is time to swarm.
This week in my winter study post it’s all about the social network. Honeybees have evolved a complex social network that involves communicating through dance, food and scents.
1 Trophallaxis (food sharing)
Unlike beekeepers who chat over tea and cake, bees exchange food and communicate by regurgitating into each other’s mouths. This makes me very thankful to be a beekeeper and not a bee!
Food sharing, or trophallaxis, is when two worker bees share the crop content (a mix of nectar and other substances) in their honey stomachs, which results in an exchange of information about each other and about the colony. The clearest account I have read of trophallaxis is given by Celia F Davis in The Honey Bee Inside Out (pages 106–7), making a potentially confusing topic actually simple to understand:
‘It starts with one worker begging for food or another offering it. A begging bee pushes its proboscis [tongue] towards the mouth of another bee. The other bee then opens its mandibles, pushes its proboscis forward and regurgitates a drop of nectar from its crop, which the begging bee takes. An offering bee will regurgitate a drop of nectar and offer it to another bee. The result of this is that the crops of adult workers throughout the colony will contain the same mix of nectar and other substances at the same concentrations.’
Celia F Davis. The Honey Bee Inside Out
This method of food exchange is very rapid. Studies found that coloured or radioactive nectar fed to a few workers was spread to more than half the workers in the colony within 24 hours.
What’s the point of trophallaxis? Well, it gives each bee the ‘common colony stomach’, says Davis, so that they all have the same smell. This is how bees from the same colony can recognise each other; for example, guard bees can recognise returning foragers as members of their colony. It also ensures that ‘all the bees in the colony have a continuing appreciation of the quality of incoming nectar and pollen sources and their abundance in the colony’, which in turn can affect:
- foraging behaviour
- brood rearing and division of labour between house (inside) bees
- queen’s rate of egg laying
Trophallaxis and other methods of communication
Trophallaxis can play a part in the exchange of scent (chemical) messages, when bees touch antennae during nectar sharing. Food sharing can also happen during the waggle dance when the dancer gives a taste of nectar to another bee to show how good it is.
Honeybees are very good choreographers and they use different dances to communicate including the DVAV, round dance, sickle dance and, everyone’s favourite, the waggle dance.
The waggle, or wagtail, dance is a figure of eight movement with a little waggle in the middle. It is performed by foraging honeybees who find a good source of forage (trees or flowers) and then fly home to tell everyone else.
It goes something like this…
The bee walks in a straight line waggling her bottom and buzzing her wings. She then turns and loops back to where she started. She walks along the straight line again, waggling her bottom and buzzing her wings, then loops back in the other direction creating a figure of eight on the dance floor. The straight line indicates the direction of the food and the number of waggles indicates the distance.
In the bee world, the vertical face of the honeycomb (imagine sections of comb hanging down inside the hive) represents the sun, and the angle of the straight line to the vertical indicates the position of the trees or flowers to the sun. For example, if the straight line is run at a 60 degree angle, then the food source is 60 degrees to the sun.
As the sun is always moving across the sky, the dancer calculates the sun’s movement by adjusting the angle of her dance every four minutes by one degree to the west.
If my clumsy attempt to describe the waggle has left you confused, then Sir David Attenborough explains it excellently in the BBC’s Trials of Life. Finding the way: waggle dance.
The round dance is performed as a simple loop. It doesn’t give directions like the waggle dance and simply says ‘Go get it!’ The round dance is used when a food source that has a particularly high sugar content is not far from the hive, for example: a field of oilseed rape, other hives or an M&M factory! There must have been a lot of excited French bees doing the round dance last year after discovering vast quantities of blue sugar syrup nearby.
The sickle dance is a figure of eight without the waggle in the middle. It is somewhere between the round dance and the waggle dance and it is used when the distance to the forage is somewhere inbetween. It says, ‘around the corner and up the next street’.
There are other dances that have been observed inside the hive.
- Jostling dance: a prelude to the waggle dance. Foragers returning from a successful trip will run and push other bees to let them know they are about to do the waggle dance.
- Spasmodic dance: a variation on the jostling dance that includes food sharing, and presumably gives the same message.
- Trembling dance: while the DVAV dance recruits more foragers, the trembling dance seems to recruit more receiver and storage bees to help foragers unload nectar and pollen. Davis says: ‘A bee runs about on 4 legs and twitches and trembles. If it meets a bee performing a wagtail dance, it head-butts it and briefly pipes.’
Apparently, the time it takes for a forager to unload her nectar influences the type of dance that is performed. If the forager takes 20 seconds or less to unload nectar, the DVAV dance is performed to recruit more workers to forage. However, if the forager takes 40 seconds or more to unload, then the trembling dance recruits more bees to help process nectar being brought into the hive.
The dance language of bees is varied and complex, and care should be taken in the interpretation, says Davis. For example, the trembling dance can also be a request for grooming. Other dances, like the DVAV dance and the buzzing run, have also been connected with swarming.
The buzzing run is where a bee runs in a straight line while buzzing its wings and collides with another bee – they touch antennae, buzz and run off to collide with more bees. The dance has a cascading effect across the hive with bees buzzing, running and colliding until they swarm. Davis says that the buzzing run is performed again by the swarm before flying off to its new home, and it is then sometimes called the break dance.
As an aromatherapist, I envy bees living in a world of aromas. The hive is like a perfume factory with a scent for every occasion, including: to communicate, to stimulate and suppress behaviour, to coordinate activities, to attract and to alert among many other things.
These important scents are pheromones – chemical substances that are secreted to affect a specific reaction. A helpful definition of pheromones was coined in the 1950s:
‘Pheromones are substances which are secreted to the outside by an individual and received by a second individual of the same species in which they release a specific reaction which may be behavioural, developmental or physiological.’
The chemicals are made in glandular cells and secreted by glands, specifically exocrine glands, that secrete substances outside the body. (Humans, for example, have an endocrine system – endocrine glands – that secrete chemical substances such as hormones inside the body. A very basic biology lesson!)
In the hive, pheromones are released by queens, workers, drones, brood and even comb. As many pheromones used by honeybees have been covered in other posts, for the purpose of this part of the syllabus here’s a quick summary:
There is so much to explore about the world of pheromones that I may revisit this in another post.
Finally, a form of communication largely used by queen bees, although sometimes used by workers, is piping and it can be associated with swarming. Virgin queen are known to pipe inside their cells and it is thought that they are warning their sister queens-in-waiting that they have a rival for the throne! After emerging from her cell, an unmated or mated queen also makes this noise by resting her thorax on the comb and vibrating her powerful flight muscles.
Visit my blog index for more winter study posts.
A great revision post from Emily Heath of Adventures in Beeland: 5th Honeybee behaviour revision post: bee communication
Mid Buck Beekeepers Association Blog’s excellent revision notes for BBKA module 6
Celia F Davis. The Honey Bee Inside Out. Bee Craft Ltd, ISBN-10: 0900147075
Ted Hooper. Guide to Bees and Honey. Northern Bee Books, ISBN-10: 1904846513