Just about everyone is aware of
honey bees (Apis sp.); the crop
pollinators, covered in fur and ever so adorable. Less people will know about
the Giant Hornet (Vespa mandarinia
japonica) that is found throughout Asia and a fierce hunter of the honey
bees being able to decimate an entire hive on European honey bees (Apis mellifera) in only a couple of
hours. They have a body size of 4-5cm, can travel at speeds of 40km/hr and has
a stinger over 0.5cm that injects potentially lethal venom and leaves a wound
similar to a bullet hole – it is responsible for over 40 deaths a year in Japan
alone. Both species are social and although a vast size and weaponry difference,
the native Asian honey bees (Apis cerana japonica)
have adapted to this predation in a very interesting way.
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| Japanese Giant Hornet (Vespa mandarinia japonica) compared to a honey bee (Apis sp.) |
V. mandarinia japonica is the only hornet species that have evolved
mass predation on other social hymenoptera (Ono et al, 1995). A solo scout
hornet will find a food source (for e.g. a honey bee colony) and will kill
individual bees to take back to their nest, after several individual kills are
made the scout hornet will mark the site with a secretion of a forging site
marking pheromone, other foraging nest mates will detect the pheromone and
begin killing individual bees as well (Ono et al, 1995). Then things get a
little brutal: once there are three or more individual hunting hornets on one
hive the hornets attack as one, with each hornet being able to kill 40 bees in
a minute with its mandibles - 10-20 hornets can kill over 30,000 bees in one massacre
lasting less than 3 hours (Ono et al, 1995).
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| V. mandarinia japonica attacking an A. mellifera hive and the pile of bodies left from the massacre. |
However, the slaughter is what is
expected (and seen) when the hornets encounter the introduced European honeybee (A. mellifera). It has been shown
that the Japanese Asian honey bee (A.
cerana japonica) is able to defend its hive from a mass attack (Ono et al,
1995). A. cerana japonica can detect
the hornets pheromone and lure the first scout hornet into the hive by teasing
it from the entrance with 100 tasty worker bees who vibrate their abdomens for
further temptation - little does the hornet know, there are a thousand bees
that have dropped their hive duties and descended from the honeycomb to lie in
wait just inside the hive opening (Ono et al, 1995). As soon as the hornet attacks a bee inside the
hive it is engulfed in a ball (‘hot defensive bee ball formation’) of bees that
vibrate their bodies, producing high temperatures (47˚C) in the centre of the
ball (Ono et al, 1995). But it is not just the temperature that kills the
hornet, oh no it gets better – the bees also produce lethal amounts of Carbon
dioxide (CO2) inside the ball that in combination with the high
temperatures kills the hornet within 10 minutes (Sugahara & Sakamoto,
2009). It has been found that mixed-species colonies of A. cerana and A. mellifera
are able to form this death ball but not as effectively as a pure A. cerana colony (Tan et al, 2011).
It is not known as yet exactly how the A. cerana japonica form the defensive ball so quickly as there is some evidence of both acoustic and chemical communication (Ono et al, 1995). It is believed that the V. mandarinia japonica evolved their mass attack as a coevolutionary strategy to counteract the A. cerana japonica defence tactic – the mass attack often works when the bee colony numbers are low, the hornet can then take over the bee’s home and can provide large amounts of food for reproductives (Ono et al, 1995).
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| A. cerana japonica in the hot defence bee ball formation around v. mandarinia japonica |
It is not known as yet exactly how the A. cerana japonica form the defensive ball so quickly as there is some evidence of both acoustic and chemical communication (Ono et al, 1995). It is believed that the V. mandarinia japonica evolved their mass attack as a coevolutionary strategy to counteract the A. cerana japonica defence tactic – the mass attack often works when the bee colony numbers are low, the hornet can then take over the bee’s home and can provide large amounts of food for reproductives (Ono et al, 1995).
References:
Ono, M, Igarashi, T, Ohno, E & Sasaki, K 1995, ‘Unusual
thermal defence by a honeybee against mass attack by hornets’, Nature, vol. 377, pp. 334-336.
Sugahara, M & Sakamoto, F 2009,’ Heat and carbon dioxide generated by
honeybees jointly act to kill hornets’, Naturwissenschaften,
vol. 96, pp. 1133–1136.
Tan, K, Yang, M, Wang, Z, Li, H, Zhang, Z, Radloff, SE,
Hepburn, R 2011, ‘Cooperative wasp-killing by mixed-species colonies of
honeybees, Apis cerana and Apis mellifera’, Apidologie,
vol. 43, pp. 195–200.
Image 1: Armstrong, WP 2012, Wayne's Word, viewed 25
May 2015, <http://waynesword.palomar.edu/images2/AsianHornet5c.jpg>
Image 2: unknown contributor (Korean site – etorrent.co.kr),
viewed 25 May 2015, <http://cdn9.pikicast.com/card/3d9b7f26-f956-4a5f-9180-8613b4b4f880_20150330173643989.jpg>
Image 3: Hypescience 2014, Hypescience, viewed 25 May 2015, <http://hypescience.com/wp-content/uploads/2014/10/abelhas.jpg>
I have long found those Japanese honey bees to be quite fascinating. They are an excellent example of how being a predator is a risky thing, as the prey can often be at least as dangerous (in this case, more so) as the predator(s) hunting them.
ReplyDeleteI'm a bit confused though as to how the hornets can so effortlessly massacre European honey bees. Even if these bees can't do the whole cooking ball of death thing, they still have stings so even if the hornets are extremely deadly predators its still surprising said hornets don't get stung to death when the bees outnumber them so much.
I believe its basically a difference in attack/defence strategies. The european bees attack the hornet outside the hive, piling out the front making themselves an easy target especially during the massacre. It seems the European bees cannot detect the hornets pheromone either and cannot prepare for the impending massacre. Due to the size difference, once the hornet has a hold on a bee they would be unable to sting before being chomped in half by the hornets mandibles.
ReplyDelete