Broodnest comb is more than a place to store food, raise brood and hang out. It has a structure that is essential for optimum colony function and survival.
When a swarm moves into a cavity, the bees evaluate it’s shape and orientation. Then they build a nest that provides the best possible chance for reproduction and survival.
The resulting broodnest structure compliments changing seasonal requirements and varied colony activities. These relationships are discussed on the Seasonal Dynamics page.
Given a choice, a colony will reject a cavity that can’t accommodate its needs.
The nest can be divided into 3 areas:
- the broodnest
- the broodnest core
- the honey storage area
When a colony decides to swarm it evaluates a cavity for suitability. Important factors include:
- cavity size
- entrance orientation
- and defensibility
Their ability to evaluate and act, doesn’t stop once a suitable cavity is found. They continue to make decisions and build a nest whose structure enhances the colony’s survival.
Nest Construction Observations
My top bar hive swarms, cluster in the first one third of the hive, nearest the entrance. Then comb building activity begins on top bars 3 to 5.
Initially, comb building is limited by the cluster’s size. There the bees feed each other and can keep the wax warm enough to work. At this point:
- most comb is extended horizontally
- a few central combs are built vertically, just beyond the clusters confines
- as more comb is built, environmental control between combs requires fewer bees, which frees more bees to work horizontally
Bees build a few large storage and drone cells along the top bars. Then they quickly transition into larger size worker cells. This transition is most pronounced on comb near the entrance.
Worker comb is quickly built there. Later, larger worker size cells and drone comb are completed on the comb farthest from the entrance.
When a few combs are long enough to shelter new brood, vertical comb building becomes more uniform and extends beyond the cluster.
Bees often shift their comb building focus. Sometimes, comb is extended horizontally. Then suddenly, the bees move towards the hive’s front and work comb vertically.
These shifts aren’t strictly related to nectar flow. I’ve seen the bees complete the broodnest core area, near the entrance, during a strong honey flow, and not work in the honey storage area toward the rear of the hive.
Broodnest structure remains consistent even when bees shift their comb building focus elsewhere. Later, a new generation return to finish out the area completing the broodnest structure started by another generation of bees.
How do different generations of bees individually sense what comb is needed? If they couldn’t sense it, each bee’s effort couldn’t produce any structure, as each bee builds only a small part of any one cell.
You can download this Google Sketchup based cross section and take a closer look:
Bees build straighter comb near the entrance:
- It’s spaced at 1 1/4 inches
- and each comb is a close approximation of its neighbor
This is the brood rearing area of the broodnest. Here cells gradually taper from larger sized worker cells:
- at 5.4mm near the top bar
- to 4.9mm half way down the comb
- to about 4.6mm near the bottom of the comb
Comb in the broodnest area is straight and parallel with the ends of larger combs curving toward the cavity’s entrance.
Bees kept the smallest cell size areas, near the entrance, open for brood rearing. And they cluster there during the winter. This is the broodnest’s core.
And it’s a important area. Here the bees:
- detect and remove broodnest peers
- conserve heat and humidity
- and efficiently use scarce late winter resources
Honey Storage Area
Farthest away from the entrance, combs quickly transition into a honey storage area. This transition is determined before the colony completes the broodnest area.
- are thicker and wider spaced here
- contain a few patches of larger worker size cells near a comb’s bottom edge
- most cells are drone size or larger
- cell orientation often appears chaotic
- no small cell sized comb
Combs are parallel in the honey storage area, but straight comb isn’t a priority. Sometimes the direction of comb is completely contrary to the broodnest comb. Here, combs often drastically curve toward the entrance.
Once the broodnest is complete, the honey storage area is extended away from the entrance until an optimum condition is reached. Then only minor broodnest construction
occurs regardless of available space or nectar resources.
Sometimes a comb is built that doesn’t follow the broodnest structure. Bees are genetically wired to orient and build the right comb, at the right location. But, it’s a delicate process with many factors involved.
Top bar 7 of my hive, was drawn as a mirror image of the adjacent broodnest comb. Drone size cells were drawn down low, on the side nearest the entrance. Worker cells were drawn on the right side. I thought a comb was mistakenly reversed when I worked the hive. Early photos show this top bar had a unique knot. The top bar orientation was correct.
The bees had trouble working with this comb. Some shots show the bees attempted to rework the comb. Combs on either side of this one were drawn rapidly and smoothly finished off. The bottom edges of this comb remained ragged and this comb was never completely finished off.
Can bees make mistakes? I think they can, especially with a beekeepers help. 🙂
This comb was within the broodnest core. The lower left part of the photo should be small cell sized worker comb to be consistent with combs on top bars 6 and 8.
The bees tolerated the drone size cell in the upper left of the shot. And they tolerated the larger worker sized cells to the upper right. But they couldn’t tolerate the drone sized cells in the small cell sized broodnest core.
A comb’s orientation and location is important. Or the bees wouldn’t have had problems with this comb.
Comb management is a delicate process. The bees balance many factors when building a broodnest. But they don’t have any mechanism to handle comb that:
- is inserted backwards
- or disappears
Typical hive management mixes up a broodnest. When I messed up the broodnest structure in my top bar hives, they quickly developed parasitic mite syndrome. And required mite treatments to survive. When I re-arranged the comb to mimic a natural broodnest structure. Mites were seen in those hives, but they didn’t developed PMS.
That’s how important the broodnest structure is. Mess it up and you have messed up the hive.