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Self-Organization in Social Insects

Self-Organization in Social Insects. Kaz Uyeharaaaaaaaaaaaaa!!!. The Basics. Insects are pretty smart, but are they smart enough to have the individual cognitive power to build complex structures and exhibit complex global behaviors? We don’t think so!

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Self-Organization in Social Insects

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  1. Self-Organization in Social Insects Kaz Uyeharaaaaaaaaaaaaa!!!

  2. The Basics • Insects are pretty smart, but are they smart enough to have the individual cognitive power to build complex structures and exhibit complex global behaviors? • We don’t think so! • Maybe the insects obey simple “if this then that” rules using local information and the result is emergent complexity! • That’s self-organization suckas! • Read my paper for more info, or take a peek at my sources.

  3. Bee Thermoregulation • Let’s look at the thermoregulation of bee swarms. • Our models are good enough to suggest that this behavior is self-organizing.

  4. Bees thermoregulate? • Honey bee colonies divide in a process called reproductive swarming. • The swarm consists of the a queen and about half the workers. They go and find a new nest site. • The swarm forms a cluster while it waits for scouts to find a suitable site.

  5. The Swarm! • The inner core of the swarm is maintained within a few degrees of 35 C, while ambient temperatures fluctuate from 1 to 25 C. • During this time, the surface temperature of the swarm is kept at 15-21 C. • When the ambient temperature reaches 16 C, the surface temperature is not regulated but averages 2 to 3 C above ambient temperature.

  6. Why Swarm? • The swarm bees have a limited store of honey (energy). So they need to save as much energy as possible for building the new comb and foraging. • The bees also have to stay warm (especially the queen) and protected from predators. • Energy is saved by allowing the bees on the outside of the cluster to be cooler. • This saves energy for the cold bees and… • Minimized the heat loss (lower temperature difference between surface and air).

  7. The Winter Swarms • A similar behavior is observed in the winter. • The bees form tight clusters to keep warm enough to stay alive. • Over ambient temperatures of -15 - 10 C, the core temperature is kept between 18 and 32 C and the mantle temperature between 9 and 14 C. • The bees die in temperature from 9-12 C, so they are REALLY trying to conserve energy.

  8. Hmmm… • It looks like these bees are operating as one super-homeothermic organism! • COULD THEY BE CONSCIOUSLY ACTING IN SUCH A COLLECTIVELY INTELLIGENT WAY?? • OR is this an example of an evolved self-organizing behavior? • … • I don’t know, but check out our models!

  9. But first... • Is the queen just telling them what to do? • Nope. Took out the queen and they still did it. • Do the bees gather information from the whole colony and then coordinate movements? • Nope. Cut off communications between bees and they still did it (not physically touching, not movement, not sounds, not in the air). • The bees can generate the “desired temperatures” when ambient temperatures are at 5 C WITHOUT changing from resting metabolic rate. • Sometimes in big swarms at low temperatures, the core bees overheat…so it doesn’t seem like the bees are THAT smart.

  10. How do individual bees behave? • If a bee gets a little chilly on the surface of the cluster, it can just move in closer and point there heads in. • This closes gaps in the swarm and the bees’ hair gets interlaced (insulation). • The bees have a special mechanism that keeps head and thorax warm even when their abdomen is cold (saves energy). • If they are really cold they can start to shiver…but it takes more energy.

  11. So… • When an individual bee gets cold, it moves in and sticks its ass out. So it lives. • But on the global scale, as these surface bees move in, core temperatures rise. So the core can get warmer when the ambient temperatures go down! THE QUEEN LIVES! • When it’s hot out, the swarm has natural ventilation shafts, as the surface bees are not densely packed…then extra heat is dissipated by fanning their wings to increase convection!

  12. Watmough and Camazine model • Two partial differential equations used to describe previous behaviors: • Heat transfer and production as a function of time, t, radial distance, r, from the cluster center, and the metabolic output of a single bee at temperature f(T) multiplied by the density of bees. • The density of bees as a function of t, r, and temperature T.

  13. The model • Used a lot of experimental data for parameter values. • Fits with observation: Lower ambient temperature --> higher core temperature. • Temperatures within observed ranges.

  14. Of course… • We need to run some experiments to test the validity of the model and test its predictive power. • Results are strong enough to suggest that this is a possibility. • Let’s watch a movie: • http://www.youtube.com/watch?v=0m7odGafpQU&feature=related • http://www.youtube.com/watch?v=JtFVQe4JRmA

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