The Bee Ball – Bee Thermal Defense

Gangs of Asian giant hornets attack bee nests, killing all the workers before stealing the larvae for food. The little bees can’t sting through the thick hornet armour. See’s 5 Most Horrifying Bugs VS Scott’s 5 Most Horrible Worms for more on that.

So instead, the Japanese honey bees use a novel defense behaviour. They cook the hornet invaders to death.

As the hornets aproaches the nest, around a hundred bees will gather at the entrance and keep it open to draw the hornets in. Once a hornet is in, about five hundred bees rush the intruder and grab onto it, immobilizing it.

The bees then start vibrating their wing muscles, producing heat and raising the temperature to 47 degrees Celcius. The bees can tolerate such temperatures, but the hornet finds even 45 degrees fatal.

Thus the smaller bees overcomes the hornet tanks with their own version of Molotov cocktails. This interesting tactic is called the ‘bee ball’, or more technically, ‘bee thermal defense’. See Wikipedia article for more details.


     Bees mobbing a hornet, which is stuck inside the ball.

You can watch a 5 minute 51 second video of a gang of big bad hornets bullying and decapitating little bees, followed by an example of bees fighting back with a bee ball attack (with a graphic of the temperature increase in the ball). Video here.


Much bigger hornet on the right, just before biting the head off a bee.


The bees in pro wresting royal rumble action! You can just see the wider stripes of the hornet contrasting with the smaller bees.


                                    Bee-ware the fire-beeball!

This really cool bee-haviour (lol) strikes me as extremely complex to evolve randomly. So How did this very complex behaviour come about through Darwinian evolution?

Here’s the hypothesis: Since evolution favours the adaptations most suited to survival and propogation of the next generation, the bees must have been subjected to a life-or-death challenge from the hornets. True, since the hornets wipe out an entire bee colony in each attack.

Some (or even only one) of the bee colonies must have had the incredibly lucky, coincidental and pure random chance quirk of its workers tending to behave like hippies giving group-hugs-for-everyone. Throwing themselves at the hornet, their hot free love happened to overwhelm the invader.

If none of the colonies at all had this chance reflex, there would be no more honey bees for hornets to prey on them. Or if the hornets had a higher temperature tolerance than the bees, the tactic would fail miserably as the overheated bees die and fall off one by one.

The few (or one) colonies with the chance successful bee balling behaviour went on to reproduce via alates (princes and princesses). Now, the queen which produced these alates must already have been lucky enough to carry genes that produced the quirky bee ball behaviour in the workers.

Some of the alates on their mating flight must be lucky enough to carry the genes for bee balling. That’s a given, seeing as how many alates are produced. Some of the gene carriers must be lucky enough to survive the subsequent mating and found a colony.

From the mating, the genes for bee balling must be lucky enough not to be overwhelmed by non-bee balling genes (which may be dominant). This problem is solved if all non-bee balling genes have already been wiped out by hornet attacks on the bee colonies.

The new colonies must next be lucky enough to survive any challenges… Including early hornet attacks (before the bee ballers are ready) and non-hornet threats. The latter is especially poignant since by selecting for bee balling behaviour over other fitness factors (such as resistance to disease), other fitness factors may be lower.

And finally, this series of happenstances must successfully continue for generations upon generations until all Japanese honey bee colonies have the bee balling behavour. One way this could happen sooner is if the hornets are especially efficient and wipe out ALL colonies with no bee balling behaviour, leaving only the few bee ballers to survive non-hornet threats and fill up the population.

A long series of lucky breaks. But go all the way back to the start… How did the complex bee balling behaviour itself evolve in the first place?

It’s not a simple matter to coordinate letting the hornet in, jumping a hornet simultaneously, and vibrating instead of stinging. Especially when the hornet can whack 40 bees per minute – no teamwork by the bees means death.

Seems a very far cry from standard bee behaviour to me. Was it merely random chance that a non-productive behaviour was not weeded out by evolution before it turned out to be a beneficial tactic against hornets?

It’s very easy to say: “The Japanese honey bees evolved the bee balling behaviour as a defense against hornet attacks.” But such a proclamation says nothing about WHERE the behaviour originated from or HOW it reached the point of usefulness from a nonsense behaviour.

Genes don’t just spontaneously appear from nowhere, as Lamarckian evolution has been disproven.

All together, a host of assumptions and fortunate happenstances are required for bee balling to evolve by random chance. Similar to the extremely complex behaviour of building 6 metre high termite mounds with excellent air conditioning.

PS. Interestingly, linked to by a Biology module.

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12 Responses to “The Bee Ball – Bee Thermal Defense”

  1. betterthanhuman Says:

    Wow! This is just awesome. Your blog is really great.

  2. ATPman Says:

    Before I start i would like to say that i enjoyed all of the interesting images you posted

    1. Genes don’t just spontaneously appear from nowhere, as Lamarckian evolution has been disproven.

    Lamarackian evolution was used to describe PHYSICAL changes in animals, not behavioral (the example i learned in college was the giraffe stretching its neck made it longer for the next generations). Genes CAN appear out of nowhere i.e. Down Syndrome (addition of a chromosome), but in this case the genes have simply changed. This isn’t evolution, but rather an instance of an adaptive mutation. In mainstream biological thought it is held that while mutagenesis is non-random in many ways, the utility of a genetic mutation to the organism in which it occurs does not affect the rate at which it occurs. However experimental evidence exists that in some instances the rate of specific mutations arising is greater when they are advantageous to the organism than when they are not.

  3. The 5 Most Horrifying Bugs in the World « in monologue Says:

    […] Those who find the bee homicide entirely too cruel, rest be assured – they have now found a defense tactic. Whod’ve thunk that! Posted by kureshii Filed in Uncategorized ·Tags: […]

  4. D. Franklin Says:


    Target identification, most bees will have a problem seeing a hornet as an enemy due to poor eyesight and lack of large quantities of carbon dioxide being exhaled from the enemy unlike a mamal which can easily be identified and fended off, thus it becomes difficult to identify the threat of a mimic such as the hornets.

    That being said if a bee colony can more easily identify the threat, due to a heightened ability to identify targets through site smell or sound they are much more likely to attack the target in mass. With this in mind the cooking effect is just a lucky side effect of a mass attack were that the defender continue to fend off the threat until it simply stops moving.

    and no I do not work in any fields related to bees, animals, genetics or predatory behavior. I’m a mill write/ wage slave, I operate a chop saw for a living .

  5. Just A Guy Says:

    Well, while I think that luck had alot to do with the behavioral adaptation required to do something like this, if it was just a side-effect of a massive assault on the hornets then I don’t think that they would bait the hornets into the nest and ambush them. They are using simple military tactics by waiting for the hornets to enter the nest before their assault, ambushes don’t occur by chance or luck they are strategy. Just my two cents.

  6. mita_aditama Says:

    i also just started my research about this behavior. defensive behavior in honey bee is very interesting because it is one of innate behavior. please guide me in my research… thanks a lot for your information. if you have any informations about honey bee and its behavior please send to my email at
    thanks for your attention

  7. mita_aditama Says:

    last time i found one colony of honey bee Apis cerana was making balling. i tried to measured the temperature inside and it was 44.2 oC. enough heat to kill a wasp Vespa sp.

  8. Colin Says:

    Maybe it was like this? The bees naturally tried to attack with everything they had. The wasp did kill all of the workers and abscond with some eggs, after all, and the whole cooking to death thing is a side effect of launching everything they have at the wasp.

  9. Dub Says:

    Did you ever think that they evolved parallel to one another. The hornet being able to dispatch a bunch of hornets with no problem probably developed alongside the bees collective behavior to use their abilities. Abilities that probably suit other purposes anyway.

  10. Scott Thong Says:

    I don’t really see the hornet’s traits as specific enough to have evolved to take on bees. Any creature of sufficient size and armour plating could massacre a hive of bees. However, the behaviour of wiping out a colony and stealing what’s left would be quite specific.

    Evolution doesn’ explain so many things. Recently, I’ve been wondering how a parent bird’s behaviour of ‘squirm around on the ground pretending to have a broken wing’ to distratc predators that near the nest could have evolved. ‘All those which didn’t have the precursors to this complex behaviour had their eggs smashed’ isn’t really a solid theory.

  11. Honey Bee Project « Seek Knowledge From The Cradle To The Grave Says:

    […] Bee Balling Video 1      […]

  12. Honey Bee Project « Iman's Home-School Says:

    […] Bee Balling Video 1      […]

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