The Swarming Behaviour of Honey Bees

Figure 2. A queen cup that was broken open showing the larvae feeding on royal jelly (A). Queen cells (cups build and capped) located around the edges of brood frames circled in red (B and C).  

Queens develop within 16 days of egg laying and the first virgin queen will be released from her cell within a few hours and up to ten days after the old queen has left, depending on the maturity of the developing queen.  In fact, worker bees can delay the emergence of a mature encapsulated virgin queen following communication via tooting and quacking sounds taking place between the newly emerged virgin queen and any other queens that are about to hatch. This communication is believed to ensure the colony of the presence of a queen following any virgin queen “after swarms” (second or third swarms) that may take place.  The rate of after swarming is related to the amount of sealed brood and the season when swarming occurs.

The segregation of the colony is also referred to as colony fission and it is a more structured process than one may think. So, the question is:

 How do honey bees decide who gets to leave and who stays?

Firstly, researcher in the 1970’s discovered that neither the young nor the old, but rather the mid-aged bees are more likely to swarm.

But there is another important factor. Queens are polygynous, meaning they mate with several drones on one or more mating flights. The queen’s female offspring, “workers”, are derived from fertilised eggs, unlike drones that carry the genetics of the queen only, from unfertilised eggs. For this reason, newborn workers can be related as full sisters or half-sisters, depending on the genetic material of the drone.  So, what does the genetics have to do with swarming?

Workers to a certain degree are able to distinguish the relatedness of larvae and between full and half-sisters, as adults. Therefore, are closely related sisters more likely to swarm together? To test this hypothesis, artificially inseminated queens of known genetics where set up in experimental colonies by Getz et al. (1982). The colonies were then left to swarm and interestingly swarming occurred in a non-random fashion, where age group and kin recognition, recognising relatedness, played an important part. The study showed that about 73% of individuals that swarmed had unfrayed wings (which was linked to younger age) and about 70% were the closest related to each other.

The authors therefore proposed that multiple matings in some eusocial Hymenopteran queens (honey bees are eusocial insects in the order Hymenoptera) can enhance the rate of colony reproduction through swarming. Usually swarming results in one primary swarm and 1-3 after swarms per original queen per year, in healthy unmanaged colonies.

 What happens once bees leave the original colony?

When the swarm first leaves the nest, the bees fly about in random directions within 50m of the original nest site. Once they settle down in a cluster with the old queen, the scout bees, approximately 5% of the swarm, search for a new nest site. Once a new nest site is “agreed on”, the scout bees guide the entire swarm of as many as 10,000 bees to the new location. 

Consequently, swarming results in a direct reduction in productivity of the original colony, due to the original colony having lost a large percentage of its workforce.

In fact, the productivity of the hive is impacted even earlier, prior to the actual swarm leaving!

What happens to the productivity of the hive prior to bees swarming?

Swarming changes the whole dynamic of a honey bee colony. The change in behaviour has been described as early as Aristotle, who wrote: “When the flight of a swarm is imminent, a monotonous and quite peculiar sound made by all the bees is heard for several days”

Generally, bees swarm because they are getting overcrowded. Not only is the population too large for their existing home, but bees also run out of storage space. Why, would you keep on shopping for groceries if your fridge and storage cupboards were full? Similarly, the level of stimulation for honey bees to gather food resources is reduced. This effect on hive productivity can occur up to several weeks before swarming takes place.

 This is where the purpose of swarm management not only applies to stop hives from swarming, but even more so can be used as a strategy to continuously stimulate bees for increased production, through honey robbing and brood manipulations, if increased production is  the goal. From a commercial honey producer perspective, once the colony thinks about swarming, honey production is compromised for the remainder of the production season.

Swarming signs

A few signs to watch out for:

• Queens cells (not to be mistaken with emergency cell cups) appear around the edges of brood frames
• Large bee population with large amount of brood present (about 50% sealed brood)
• No space for new food stores

Swarm prevention

• Add more space – e.g. by adding a super
• Restructure the hive – e.g. brood manipulation
• Ventilation to decrease overheating
• Split the hive
• Remove swarm cells (too late, as prevention is better than stopping)

Managing swarms has now become even more important with varroa. Every swarm that leaves a hive will become a source of varroa reinfestation to our managed hives. This means increased treatments needed to control varroa and higher costs.

Let’s work together to control swarms!

References

Aristotle. The Works of Aristotle the Famous Philosopher Containing his Complete Masterpiece and Family Physician; his Experienced Midwife, his Book of Problems and his Remarks on Physiognomy. (J. A. Publishing, 2018).

Breed, B. Y. M. D. (1983). Nestmate Recognition in Honey Bees. Animal Behaviour, 311, 86–91.

Free, J. B. & Winder, M. E. (1983). Brood recognition by honeybee (Apis mellifera) workers. Anim. Behav. 31, 539–545.

Getz, W. M., Brtickner, D., & Parisian, T. R. (1982). Kin Structure and the Swarming Behavior of the Honey Bee Apis mellifera. Behavioural Ecology and Sociobiology, 10, 265–270.

Janson, S., Middendorf, M., & Beekman, M. (2005). Honeybee swarms : how do scouts guide a swarm of uninformed bees ? Animal Behaviour, 70, 349–358. https://doi.org/10.1016/j.anbehav.2004.10.018

Lensky, Y., & Haim S. (1980). ‘The effect of volume, ventilation and overheating of bee colonies on the construction of swarming queen cups and cells’. 67(1) Comparative biochemistry and physiology. A, Comparative physiology 97.

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Sagili, R. R., Metz, B. N., Lucas, H. M., Chakrabarti, P., & Breece, C. R. (2018). Honey bees consider larval nutritional status rather than genetic relatedness when selecting larvae for emergency queen rearing. Scientific Reports, 8. https://doi.org/10.1038/s41598-018-25976-7

Seeley, T. D., Morse, R. A. & Visscher, P. K. (1979). The natural history of the flight of honey bee swarms. Psyche, 86, 103–113.

Winston, M. L. (1980). Swarming, after swarming and reproductive rate of unmanaged honeybee colonies (Apis mellifera). Insectes Soc 27 : 391-398.

Winston M. L.., Otis GW (1978). Ages of bees in swarms and after- swarms of the Africanized honeybee. J Apic Res 17:123-129.

Wright, G. A., Nicolson, S. W., & Shafir, S. (2018). Nutritional physiology and ecology of honey bees. Annual Review of Entomology, 63(1), 327–344. https://doi.org/10.1146/annurev-ento-020117-043423