Saturday, March 27, 2010

Evolution of worker bee gang defense

On page 112, Jerry Coyne highlights the mechanisms involved with the battle between the Asian Giant Hornets and the honeybee colonies. As their only defense, the bees are able to "quickly raise the temperature inside the ball to about 117 degrees Fahrenheit," all by "vibrating their abdomens." (112) Coyne goes on to say that this behavior is encoded "in a brain smaller than a pencil point." (113) It is obvious that the hornets evolved to acquire their aggressive behavior before the bees needed their defense against that specific action, yet the bees' maneuver is so complex and genius that even an expert in evolution would have trouble decoding the steps needed in the evolution of that behavior. "Bee" the evolution expert, and put forth what you think is the most logical series of evolutionary improvements and milestones in bee behavior that all culminates in their current defensive maneuver of creating a vibrating oven.


  1. First of all, it is imperative to note that it is the Japanese honeybee, not the European honeybee, that has this defense mechanism against the Asian giant hornet. The Japanese honeybee’s strategy is really, really cool, and “is stunning-another marvel of adaptive behavior” (Coyne 112). However, note that the reason why the European honeybee does not have a defense mechanism is that it did not evolve in the same area as the Asian giant hornet, and as such, does not have a means of defending itself in the areas where it is an introduced species. So, logically, one can assume that the evolutionary history behind the Japanese honeybee defense is based in the fact that they evolved in much the same area as the Asian giant hornet, and is much better suited towards surviving and reproducing in such an area due to this. Simply enough, they co-evolved together, developing complex strategies to counter domination by one species or the other. This claim is backed up by an article published by the NPG (nature publishing group), which stated that the interactions between the two organisms “are specifically coevolved” (Ono et al). That’s why the European honeybee is so easily massacred by the hornet: it did not develop around the same area as the hornet, and is not accustomed to its presence in its natural habitat characterized by its lack of defense.

    However, we have still not yet proven how such a behavior could arise in bees, knowing that the action is extremely complex and some very specific circumstances must have existed for it to come into being. Then, it occurred to me that the adaptation for these bees to kill a hornet is very similar to one adaptation that is seen for heat regulation in humans. Can you guess what it is? Shivering! Along with vasoconstriction, shivering is a tactic used by humans when the environment gets too cold and heat must be generated to keep thermal homeostasis. The muscles contract and release at a fast rate, causing great output of heat, and thus warming the body at the expense of stored energy. Even though humans and honeybees are two very different organisms, it is important to note that certain behaviors are shared, and shivering is one of them. Even European honeybees shiver to regulate heat, yet have not developed the same defense mechanism because the lack of exposure to an enemy that must be killed. Then, that must be the missing link. At one point or another, some bee colony was more fit to continue surviving and reproducing because one chance encounter with a hornet while the bees were shivering caused the hornet to die, and those bees to continue living, favored by the environment, and thus pass on their genes caused by a random encounter. After all, Richard Dawkins said it best, as genes are selected through "non-random survival of random traits" (Coyne 119), and the shivering transforming into killing a hornet by cooking it is very likely a perfect example of this.

    If you want to see this defense mechanism in action, I actually just found a YouTube video explaining the process, from National Geographic. That link is in the sources section below.

    Page 112 of the book
    Page 119 of the book

  2. I agree with Mike in that the main reason for why Japanese honeybees were able to evolve in this manner and create a magnificent defense against the Asian giant hornet is because of the environment in which they live. There are no hornets present in Europe, so European honeybees don't have the need to create such a defense, and so when they do get attacked, they are immediately slaughtered off. However, the Japanese honeybees are situated in an area where they are frequently fighting off different predators, so throughout the course of evolutionary time, they created a successful defense. According to a recent study published in the journal Naturwissenschaften, scientists have found that carbon dioxide plays a role in this lethal process. The research team gave anesthesia to giant hornets and fixed them to the tip of either a thermometer probe or a gas detector. The probes were then touched to the bees' nest, and as the temperature inside the bee ball increased to more than 45 degrees Celsius, the carbon dioxide level also rose sharply as the hornets died off. Doctor Fumio Sakamoto, one of the authors of the study, said that he was not sure whether the bees were gassing the hornets with carbon dioxide or simply depriving them of oxygen, but either way, this maneuver is lethal to the hornet.