September 10, 2019
Article written by Derek Mitchell, The Conversation
View the original article here.
Credit: Aleksandr Gavrilychev/Shutterstock
Despite the importance of nests to honey bees, the hives we build them bear little resemblance and have few of the properties of the natural tree nests European honey bees evolved with. In the 21st century, we’re still using hives designed in the 1930s and 1940s, based on ideas from the 1850s. Natural nests were only scientifically surveyed as recently as 1974 and research into their physical properties only began in 2012.
Man-made hives are squat and squarish (for example 45cm high), constructed from thin wood (under 2cm thick) with large entrances (around 60cm²) and often large openings of wire mesh underneath. They were designed to be cheap and for beekeepers to easily access the bees and remove the honey. In contrast, European honey bees evolved with natural tree nests that are on average tall (around 150cm), narrow (20cm) with thick walls (15cm) and small entrances (7cm²).
In order to assess how well man-made hives recreate the conditions of natural nests, I needed to measure the flow of fluids (air, water vapour and heat) around them. To do that, I turned to an aspect of physical science and engineering called thermofluids, the study of liquids, gases and solids of combustion, and changes of state, mass and energy movement.
In the honey bee nest, this means the “combustion” of sugars in honey and nectar, the evaporation and condensation of water, and air flow through the nest. It also includes everything being transported by the honey bees through the entrance or leaking through the walls.
The various barriers that honey bee nests create can be used as convenient boundaries in mathematical models of the energy needed and humidity produced inside the nest. My new study combines these models with data from experimental research on the thermal properties of honey bee nests and hives and behavioral studies on how honey bees ventilate their nest.
This enabled me to compare the average humidity in man-made hives and tree nests with that needed by honey bees and their parasites. I found that most man-made hives have seven times higher heat loss and eight times bigger entrance size than tree nests. This creates the lower humidity levels that favor the parasite.
My research shows the role of the honey bee nest is clearly far more sophisticated than just simple shelter. Simple changes to hive design in order to lower heat loss and increase humidity, for example using smaller entrances and thicker walls, could reduce the stress on the honey bee colonies caused by Varroa Destructor. We already know that simply building hives from polystyrene instead of wood can significantly increase the survival rate and honey yield of the bees. More research into the thermofluidic complexity of nests would allow us to design the optimal hives that balance the needs of honey bees with their human keepers.
