The bees that mummify beetles alive

By Ed Yong | May 30, 2011 9:00 am

In Australia, the penalty for burglary is several years in prison. But that’s for humans. For the small hive beetle, breaking and entering into the hive of stingless bees carries a far harsher sentence – being mummified alive in a sticky tomb of wax, mud and resin.

Small hive beetles are notorious pests. They invade the hives of bees, eat their stored food, and kill their young. In Africa, where the beetles come from, honeybees know how to deal with these pests – they wait until the beetles are in a confined space, and then imprison them within tombs of resin. But the beetle has invaded other continents, where bees are less adept at getting rid of them. In North America and Australia, it has become a serious pest, and can wipe out entire colonies.

The worker bees don’t sit idly by. They vigorously attack the beetles, but to no avail. When the beetles are attacked, they adopt a “turtle defence posture” by lowering their heads and withdrawing their legs under their hard body armour. They create an impenetrable dome that no bee can bypass. Eventually, the workers abandon their assault, and the beetles scurry deeper into the hive.

Stingless bees (Trigona carbonaria) – a native of Australia – use a different tactic. Mark Greco from the Swiss Bee Research Centre found that some workers immediately start coating the beetles with batumen – a mixture of wax and resin that they use to build their nest entrances. All the while, their hive-mates attack continuously, trapping the beetles in their own defensive posture. They can’t expose themselves or they’d get torn apart. Instead, they are forced to stay stock still, while the bees mummify them in their own armoured shell.

To see whether this defence actually works, Greco marked ten beetles with barium sulphate and let them loose at the entrance of five bee hives. These hives weren’t in their usual setting – Greco had placed them inside a medical CT scanner.

When people go for CT scans, they drink a cocktail of barium sulphate so their digestive tract will be easier to see. Greco used the same tactic to track the beetles. Every five minutes, he used the CT scanner to create a three-dimensional reconstruction of the hives’ interiors. In these scans, the barium-marked beetles stood out like beacons. Greco found that even though some beetles managed to make it into the hive, all of them had been completely immobilised within 10 minutes. That’s a far more effective strategy than even the resin tombs of African honeybees.

How is it that stingless bees, that only share a brief evolutionary history with hive beetles, have such an effective defence? Greco thinks that the tactic evolved in response to other threats, other species of beetles that could harm the hive.

Reference: Greco, Hoffmann, Dollin, Duncan, Spooner-Hart & Neumann. 2011. The alternative Pharaoh approach: stingless bees mummify beetle parasites alive. Naturwissenschaften http://dx.doi.org/10.1007/s00114-009-0631-9

More on bees:

And more on the small hive beetle:

Comments (7)

  1. Abie

    Remarkable strategy !

    And as a sidenote: I think you meant “bitumen”, not “batumen”.

  2. I meant batumen, which is what stingless bees use to build their nests. Bitumen is a sticky, tar-like form of petroleum. Bees can make honey. They can make wax. They have, as yet, not figured out how to refine crude oil.

  3. However, bees will waggle-dance to indicate the range and bearing to a particularly good tire sale.

  4. In apiculture class, the prof showed us pics of animals that had found their way into hives and been entombed in propolis – including a snake! – although no-one knew for sure if the honeybees killed/immobilised the animals or just covered up the carcass.

    FAR more interesting in my opinion was a study he carried out to see if high voltage power lines affected insect populations. A row of hives were placed at various distances from a megavolt power line. In all but one, the bees were unaffected. In the hive directly underneath the power line, the bees sealed the entire inner surface of the hive with propolis.
    Sadly it was concluded that the impact of high voltage power lines on insect populations was minimal and the work was never followed up. :(

  5. Pasqual

    Bees can entomb living and dead animals in a similar fashion. In the event that a large predator, like a wasp, enters the hive and is actively killed by the bees, or dies – maybe like the snake (too much heat, not enough air?) – and the bees are unable to remove the corpse, due to its size, they will entomb it in propolis in order to prevent the contagious elements of decay from spreading to the entire colony and destroying it.

  6. Wow simply wow!

  7. usul

    @Ed Yong, when bees DO finally figure out how to refine crude oil, imagine how much more industrious they will become. They are already highly regimented and organized with the good of the hive at the forefront of their existance. Give them a (thermodynamically) cheap and dense energy source and watch out…

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