Slumber in a cell: Honeycomb used by honey bees for food, brood, heating… and sleeping
ABSTRACT: Sleep appears to play an important role in the lives of honey bees, but to understand how and why, it is essential to accurately identify sleep, and to know when and where it occurs. Viewing normally obscured honey bees in their nests would be necessary to calculate the total quantity and quality of sleep and sleep’s relevance to the health and dynamics of a honey bee and its colony. Western honey bees spend much of their time inside cells, and are visible only by the tips of their abdomens when viewed through the walls of an observation hive, or on frames pulled from a typical beehive. Prior studies have suggested that bees spend some of their time inside cells resting or sleeping, with ventilatory movements of the abdomen serving as a telltale sign distinguishing sleep from other behaviors. Bouts of abdominal pulses broken by extended pauses (discontinuous ventilation) in an otherwise relatively immobile bee appears to indicate sleep. Can viewing the tips of abdomens consistently and predictably indicate what is happening with the rest of a bee’s body when inserted deep inside a honeycomb cell? To distinguish a sleeping bee from a bee cleaning cells, eating, or heating developing brood, we used a miniature observation hive with slices of honeycomb turned in cross-section, and filmed the exposed cells with an infrared-sensitive video camera and a thermal camera. Thermal imaging helped us identify heating bees, but simply observing ventilatory movements, as well as larger motions of the posterior tip of a bee’s abdomen was sufficient to noninvasively and predictably distinguish heating and sleeping inside comb cells. Neither behavior is associated with large motions of the abdomen, but heating demands continuous (vs. discontinuous) ventilatory pumping. Among the four behaviors observed inside cells, sleeping constituted 13.5% of observations. Accuracy of identifying sleep when restricted to viewing only the tip of an abdomen was 86.6%, and heating was 73.0%. Monitoring abdominal movements of honey bees offers anyone with a view of honeycomb the ability to more fully monitor when and where behaviors of interest are exhibited in a bustling nest.
This set of R scripts conducts all of the visualization and statistical analysis for the Slumber in a Cell project.
Getting Started Download the data files associated with this paper, and edit your file paths to execute the code using the files.
Prerequisites, Installations Install the R programming language from https://www.r-project.org/. Then install R Studio from https://rstudio.com/products/rstudio/download/. You’ll also need certain R packages, which can be installed through R. Packages needed include tidyverse, dplyr, lubridate, ggplot2, reshape2, extrafont, plyr, scales, lmerTest, emmeans, and lme4. Use the following as an example of how to install packages in R:
Install.packages(“tidyverse”)
Running the tests For Mac, use Cmd + Enter to execute a line of code. For Windows, use Ctrl + Enter. Execute each line or execute it all at once by selecting all of the script and hitting the above keys. Some plots and text files will output as saved files. Indicate your desired path for saving the files, then look for them in that directory on your computer. Other results will be output in the terminal, and should be viewed as they are executed line-by-line.
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Authors: Kathryn Busby – Wrote and designed scripts and statistical tests – github.com/katbeescience, and Barrett Klein – Design of figures and statistical tests – pupating.org
License This project is licensed under the MIT License - see the LICENSE.md file for details
Acknowledgments Thanks to Dave Reineke, Jeff Oliver, and Keaton Wilson, who contributed ideas, code, and much consultation to this project.