Expanding on the colony growth model

The first run at modeling bee colony population growth through a season was meant to validate some of the math and get a rough idea of how it would all work. Once the framework was in place the job becomes one of accounting for more details. The single biggest detail missing from the original math set was incorporating drones into the colony growth.

Much of the reading I’ve done both online and in books, many folks tend to view drones in a colony as a waste of resources, they produce no honey and do no work in the colony. All they do is eat, and fly out. This view may be correct for folks that have an outlook of ‘honey produced this season’ and they buy in all the queens they need over time. But if we raise our own stock and have an outlook that looks beyond the results of this year, the drone population we raise in this season is a very important component of our results the following season. Those drones will mate with the queens we raise this season, so they are providing half of the genetic input to our bee population next year. So while some folks view drones as a drag on the colony, my own person view is, our drone crop this year is responsible for a good honey crop next year. Another place where drones actually help the colony is during the spring buildup. While the drones are out flying during the day, overnight they are in the cluster, and that cluster is incubating the early brood rounds when nights are cold. The drone population can and does help incubating brood overnight.

The drones live on a different life cycle as compared to the worker bees, and it is very important to model this different cycle correctly. A drone egg is laid, then emerges as a larvae 3 and a half days later, just like the worker bee. The drone cell is capped on day 10, so it sits open for a day longer than a worker, then emerges on day 24. This is a critical difference as the drone cell is capped for 14 days vs the 11 days for which a worker is capped. After the drones emerge, they spend a week or two hardening and maturing in the colony before they start making regular afternoon flights to the drone congregation area. This is another important detail, because it tells us about our ability to successfully mate a new queen. You cannot successfully mate a new queen till a couple weeks after you see the first drones on frames in the colony.

So, when do the bees start raising drones ? Just about everything I’ve read on the subject suggests that the bees will start raising drones later than when they start raising workers during the early spring buildup. But this is not what we see in our hives here in Campbell River. Our bees typically start the first round of brood in the mid February timeframe, and that’s about the time we will start to consider spring feed in the form of patties. We dont normally go deep into the hives lifting frames to inspect until mid to late March. On the late March first inspection, we often see some drones walking on the frames, not a lot, but there are some. If we do the math on drone development time, seeing drones on the frames in mid March suggests they were laid as eggs in mid to late February. I am convinced the first drone eggs are indeed placed in cells as soon as the first round of replacement bees is started.

How many drones do the bees raise ? Again, reading literature provides a wide range of numbers, really depends on ‘which book did you read’ to get a handle on that number. I’ve seen numbers as low as 5 percent, and as high as 20 percent. Our own experience in looking at colonies where we place a drone frame, bees tend to fill one side completely, and the second side partially, which works out to approximately 10 percent of the brood is drone cells.

Another detail that we need to account for is drone eviction. It’s well known, as we get into the later part of the season, worker bees evict the drones from the colony. With no basis other than ‘it makes sense’, we need to consider another important date then when modelling hive populations. If the bees are evicting the living drones on a given date, when did the queen stop laying eggs in drone cells ? It takes 24 days for a drone to develop from egg to emerging bee, so it does make sense to assume that no more eggs are placed in drone cells when we are 24 days before the date at which the bees will evict drones.

After going over all of the numbers I’ve seen over time, and trying to make a realistic mathematical model for colony development, I chose to model drones by having the queen place 10% of the eggs into drone cells while she is laying eggs, and stops laying in drone cells 24 days prior to the date when the bees evict the drones. The way eviction is modelled, on days after the start of the eviction process, half of the remaining drone population gets evicted from the colony, resulting in a drone population that declines rapidly once eviction starts.