After the Swarm

Swarming is a risky business for honey bees. The swarm bees may not find a suitable new residence and perish in bad weather. For the stay at home bees it is critical their new queen mates successfully and returns safely to the colony. However for bees the benefits of swarming outweigh the risks, as colonies can potentially double their numbers with each swarm.

In the May Bee Bulletin we investigated the behaviour of bees preparing to swarm. This month we analyse the behaviour of bees after the swarm, a period during in which the future prosperity and indeed very survival of the colony hangs in the balance. We’ll show how hive monitoring provides valuable insight to aid management of the colony through this critical period.

So let’s start our story with the swarm bees leaving the hive. They will do this when there are capped queen cells in the brood nest so they can be confident that at least one of the developing queens will reach maturity, mate, and take over from her mother, who has departed with the swarm. It takes 16 days for a queen bee to develop from egg to emergence. The first queen will crawl out of her cell about 7-9 days after the swarm (depending on how long before the swarm the queen cell was capped). She will immediately set about killing her competitors for the crown before they can emerge from their cells. To find other queens she will ‘pipe’ or ‘toot’, and the queens still in their queen cells respond with a ‘quack’.  It is believed that piping is a form of battle cry to competing queens, announcing their willingness to fight to the death. You may have been lucky enough to hear the ‘piping’ of virgin queens, however if not you can listen to one of our recordings: Queen piping toot and quack

For the next 5 or 6 days the surviving queen will eat and build up for the all-important mating flights. However it may be up to 2 weeks before this happens if the weather is poor. Unlike most organisms that mate repeatedly for the production of each offspring, the honey bee queen mates once for a lifetime of egg laying.

The mating between drones and a virgin queen takes place away from the colony, in mid-air mating sites called Drone Congregation Areas (DCA’s). The drones wait for the arrival of virgin queens in these specific locations, and locate the queens visually and by pheromones.  The same place can be chosen as DCA for many years. A DCA that was first recorded in 1795 at Selborne – Hampshire (UK) by the naturalist Gilbert White is still an active DCA today, 225 years later! (Find out more)

A New Queen Reigns

The future of the colony hangs in the balance during the mating flight, will the queen mate successfully; indeed will she return at all? It is estimated that 10%-20% of queens are lost on mating flights. It has been observed that while the queen is on a mating flight the bees in the hive will fan the air with their wings across raised abdomens. It is believed that this is done to help guide the queen back to the hive by blowing out a plume of pheromones.

Bees Fanning

Bees Fanning

The entire colony may participate in this fanning, demonstrating the importance to the colony of the mating flight. We have been able to identify this behaviour with our acoustic monitoring, as we can specifically identify fanning noise. This fanning behaviour can therefore be used to identify the actual days when the queen is on a mating flight!

 

Examples from some of our monitored hives are provided below. The first graph shows a colony that swarmed on 7 May, as identified by the drop in weight (and noted by the beekeeper). The queen would be expected to emerge 8 or 9 days after this swarm, around the 15/16 May, with the mating flight taking place 5 or 6 days later, around 20/21 May. When fanning noise (blue line) is added to the graph it clearly shows 2 large peaks in fanning noise at the colony on 21 and 22 May. This indicates that the queen went on mating flights on both these days.

Graph 1: Hive Weight and Colony Fanning

Graph 1: Hive Weight and Colony Fanning

Further insight can be gained by adding cumulative rainfall to the graph (light blue line, graph 2 below), this also shows that there was wet weather from 15-18 May however it was dry on 21 and 22 May.

Graph 2: Hive weight, fanning and rainfall

Graph 2: Hive weight, fanning and rainfall

This pattern has been identified on other monitored hives after a swarm. The graph below shows a colony which first attempted to swarm on 21 June, but the swarm returned to the hive. This can be identified by the sharp decrease and then increase in weight as the swarm bees left and then returned to the hive. The colony then swarmed again on 26 June, this time successfully (both swarms recorded by the beekeeper).

Graph 3: Hive weight showing swarms

Graph 3: Hive weight showing swarms

By zooming out on this graph and adding brood temperature, it shows how this starts to drop and become unstable around the time of the second swarm; although there would still be some brood from the previous queen it would be decreasing in size quickly. The graph clearly shows that brood temperature starts to stabilise to 32°C on 8-10 July, then reaching 34°C on 12 July, thus confirming the new queen had mated successfully and is laying eggs. This was corroborated by an inspection on 12 July which identified eggs and larvae. This would indicate the queen started laying about 7 July. Working backwards from this date, this would suggest the queen mated around 4/5 July.

Graph 4: Weight and Brood temperature

Graph 4: Weight and Brood temperature

Working forward from the date of the swarm on 21 June, it would be expected that the new queen would emerge around 29/30 June, with the mating flight around 5/6 July. If we plot fanning noise (purple line; graph 5 below) it can be seen that there is a large peak in fanning on 5 July. There is also increased fanning on 1 July, but this is the result of a hive inspection (as recorded by the beekeeper).

Graph 5: Hive weight, brood temperature and fanning noise

Graph 5: Hive weight, brood temperature and fanning noise

It is also useful to check the weather over this time period, to see if this supports the timeline. Adding cumulative rainfall (light blue line) shows that there were days of rain before and after 5 July, but that on that day it was dry.

Graph 6: Hive weight, brood temperature, fanning and rainfall

Graph 6: Hive weight, brood temperature, fanning and rainfall

Finally, it is possible to look at the weather conditions on the day of the mating flight in more detail. By adding temperature in the sun and shade we can see how warm and sunny it was, an important factor for effective queen mating. The graph below has zoomed in on the day of the mating flight on 5th July, and shows that it was a warm and sunny day as temperature in the sun is higher than in the shade. The previous day was cooler and cloudier, with little difference between sun and shade temperatures.

Graph 7: Hive weight, fanning and weather conditions

Graph 7: Hive weight, fanning and weather conditions

This shows how the ability to overlay readings from multiple sensors can build up a picture of the status of a colony. Here, using weight, brood temperature, fanning noise and weather we can remotely follow events at the hive through the critical period after a swarm. We can see when the swarm happened, when the queen went on her mating flight, what the weather conditions were like and that she returned safely and started laying.  All is well, take a deep sigh and relax!