The bees run some impressive feats. Not only do they remember the location of good food sources, but they are able to communicate this information to their peers. They also take care of their young and organize attacks against intruders.
They are great builders, too. Almost every honeycomb in the cell is a perfect hexagon, and each side has the same length. This is despite the fact that bees have to build hexagons of different sizes for workers and drones, often incorporating honeycombs that started on the opposite walls of the hive. How do they manage these complications?
A new paper uses an automated image-analysis system to identify the different ways in which bees manage these transformations. The researchers who made the system found that the bees see problems coming in advance and begin to make smaller adjustments, which, in the end, help avoid the need for larger changes.
The bees in question are honeybees, although a number of other species create hexagonal structures. Regularity of hexagonal matrices of honeybees has been observed since the 5th century AD, and more recent measurements indicate very little difference between them: each side of the hexagon is usually very close in length to the others.
This happens despite a number of major challenges. First of all, many workers contribute to the constructions of each honeycomb, so regularity cannot be explained only by the involvement of a single worker in a series of instinctive movements. Additionally, nests need two different sized honeycombs, as they use distinct sizes for workers (most of the nest) and drones (males used for breeding). Finally, honeycombs are often built as multiple units, starting with different areas of the hive and eventually converging in the middle somewhere.
To find out how to manage all these issues, animal behavior specialist (Michael Smith of Auburn University) met up with two computer scientists from Cornell University: Nils Knapp and Kirsten Petersen, who are working on insect-like robots. Together, they put together image analysis software that could determine the boundaries of each cell, and discovered basic stats for the cells—the number of sides, the length of each side, etc. They can then be categorized based on whether they are the right size for workers, drones, or if there is something unusual in the cell.
Organized transfers and more
Most of the cells in a particular comb were the offspring that needed the most. This means workers, and they are usually smaller. But before they start building cells for the drones, workers will start building cells that are slightly larger, allowing for a smooth transition in size. This transition only required two cells to operate, and it covered an area smaller than the reach of a worker’s legs.
Managing the integration of the different honeycombs was considerably more difficult. This happens when cells with an unusual number of sides end up being needed. The image recognition system identified cells anywhere from four to nine walls, rather than the typical hexagon shape. These were rare, accounting for less than 5 percent of all cells in the honeycomb. But it tends to occur either at the edges of the comb or in separate lines where two combs are fused.
Even when it was not possible to form a six-sided hive, the bees tried to get as close as possible, as 93 percent of the anomalies were either five or seven-sided. Often, the two have been paired together; Boundaries between five- or seven-sided cells were more frequent than in pairs of two-pentagons or two seven-sided cells.
One of the main reasons these individual hives are necessary is that the bees will start building in different locations by making honeycombs of different orientations. Thus, as these different segments grow to meet each other, the hex matrices will be oriented at incompatible angles. The larger the angle, the greater the need to use non-hexagonal cells. In extreme cases, more than half of the cells along the line where the honeycombs fuse have something other than six sides.
But the bees were able to see the problem coming, and they started twisting the hexagons before the different honeycombs met.
Is this realization?
The researchers accurately summarize what they saw.
“The bees effectively ‘roll’ the hexagonal cells into the gap when combs are combined,” they wrote. “If the tilt difference is small, these rolling cells can maintain their hexagonal shape, but when the tilt difference is large, bees use non-hexagonal shapes to fuse the combs.” And remember, it’s all layered over the complexity of managing two different cell sizes.
All this, for the authors, indicates that the process of comb building is not purely instinctive. There must be what they call “cognitive processes” involved in the construction. The bee brain is a far cry from anything we understand very well (the closest species we know closely is probably the fruit fly fruit fly). This makes figuring out what those processes might look like.