Friday, September 19, 2008

Shimmering Repels Hornets from Honeybee Nest

Giant honeybees (Apis dorsata) have evolved an impressive looking defence mechanism that effectively deters one of their predators, the hornet. The behavior termed 'shimmering' involves hundreds of bees flipping their abdomens upwards rapidly in a wave that spreads across the surface of their open nest. Shimmering is not only a reliable survival strategy but it is one that involves very little risk on the part of the honeybee and consumes far less energy than sending out flying defenders or "heat-ball"ing intruders to death.

Small-scale waves prevent the hornet from being able to single out one bee and a failed attack results. As the number of bees involved in the wave increases the hornets turn further away from the surface of the nest and increase their speed of retreat. There is a definite limit to the level of protection that shimmering offers however. This limit is called the mean hovering distance and is determined by the experimental distance at which the hornet displayed an avoidance reaction to shimmering. Just as the hornets responded differently to the intensity of the shimmer the honeybees shimmer is a result of the location and speed of the hornet. A faster hornet in closer proximity to the nest elicited a stronger, faster wave pattern.

An important part of this process is the hornets inability to adjust its behavior to the repeated failings of its attacks. Shimmering stimulates a fixed action pattern of avoidance in the hornet that it is unable to habituate itself to.
The authors of this paper Gerald Kastberger, Evelyn Schmelzer, and Ilse Kranner also included this brief discussion of the pheromone cues of shimmering:
Stinging activities do not occur during shimmering, but otherwise,
alarm pheromones of honeybees do not prevent hornets from hunting bees
[2], [17]. Second, shimmering is accompanied by the
release of Nasonov pheromone
[14]. After a series of repetitious waves, Giant
honeybees open their last inter-tergital gaps of their abdomens, exposing the
Nasonov glands. Nasonov scent is a social pheromone and signals to the bees to
‘stay together’
[14], thus preventing single bees from changing
their roles into those of guard bees (flying defenders) that would fly off to
attack the predator. However, there are reasons that make it is impossible for
Nasonov pheromone to trigger the avoidance response of an approaching hornet.
Firstly, the exposure of Nasonov glands has been only observed after a series of
shimmering episodes
[14], but hornets were disturbed by shimmering
from the first wave onwards. Additionally, and more important is that the
latency of the avoidance reaction of the wasp after the onset of shimmering is
less than 100 ms, and is therefore by several orders of magnitude faster than
the exposure of Nasonov glands and also faster than the obvious spreading of the
pheromone would take.
Posted by: Margaux Curboy (1)

Update 09/23/08:

Here are some videos used in the study to visually clarify the idea of shimmering.

Mexican Wave
New Scientist briefly explains four videos used in study.


At 12:50 PM, Anonymous Anonymous said...

I am a little confused on what "Shimmering" actually does. You explain how the defense mechanism is performed but what about this causes the hornets to not attack. I am also curious as to what "Heat-balling" entails as it is mentioned by name but not fully explained.

Posted by: Alex Jackson

At 1:12 PM, Anonymous Anonymous said...

I really liked this article. It interesting that such a small creatures like the honeybees can work together to thwart of intruders. Do they shimmey only in the presence of hornets? Will shimmering work on other intruders? Maybe you could describe shimmering a little bit more, I think readers will be interested in it. Great article though!

Mia DiFabbio

At 5:02 PM, Blogger PWH said...

I find it amazing that honey bees can work together to ward off the hornets, especially since the hornets do not have the ability to adjust to it. Since this is a fixed action pattern and I am wondering how many attempts they take at attacking before giving up.

Tara Quist

At 3:20 PM, Anonymous Anonymous said...

Hi there, by shimmering do you mean they have more reflection on their abdomens that refracts the light to blur their bodies together? That's what I imagined when I read this. I'm also confused by what is meant by "heat-balling". Also I'm confused when you say they release the Nasonov hormone which makes them stay together after they are already working together to stave off the hornets. I would assume they release the hormone at the initial cues of a hornets attack. Great job, just need to explain a bit more.

Posted by: Ashley Maillet

At 4:10 PM, Blogger PWH said...

its very interesting, hundreds or thousands of bees in harmony, keeping away a predator. i just wonder if this is a technique the honeybees use only against the hornet or a variety of predators?

-Hessom Minaei

At 4:34 PM, Anonymous Anonymous said...

Hey, I think I've seen video clips of "shimmering" bees before. It's hard to describe unless you can see it. I was wondering why this reaction is specific to hornets? Are the other mechanisms like "heat-balling" also specific to certain predators?

-Jane de Verges

At 7:11 PM, Blogger PWH said...

Interesting article. I've never heard of this type of behavior from honeybees before! In the article blurb at the end of your post, it mentioned an alarm pheromone given off by honeybees when a hornet is approaching. Is this is the releaser for the fixed action pattern of "shimmering"? Also, what then is the sign stimulus for the alarm pheromone? How does a honeybee detect the predator? Does one do it or do many?

Maura Mulvey

At 7:40 PM, Anonymous Anonymous said...

I kind of understand what shimmering does but not quite. Does it only require a large group of bees to scare off their predators? What if only one bee performed it, would the hornet run off? Is hornets the only predator that gets confused from shimmering?

Very interesting article btw.

- David Huynh

At 9:33 PM, Blogger PWH said...

I found this article interesting. The honeybees use a defense which triggers a FAP in the hornet. I wonder if the hornets will ever learn to disassociate the honeybees "shimmering" with their FAP

Charles Scondras

At 8:38 PM, Blogger PWH said...

I had no idea that hornets attacked Bees. What do hornets get out of attacking them? Anyways, this survival strategy. From what I understand, shimmering tends to repel most hornets. If the hornets aren't repelled back, the social hormone release in the honey bees disables them from moving out of their spot, and the honey bee that is targeted by the hornet pretty much takes one for the team and gets killed by the hornet. I think thats what is happening anyways. If this is the case, shimmering allows Honeybees to sacrifice one of their members for the good of the whole. This type of defense can be found in many species.

Patrick Salome

At 10:18 PM, Blogger PWH said...

Nice article! Bees are fascinating insects. I was curious as to what other defense mechanisms do these giant bees have against predators. Do the hornets eat the bees? Or are the hornets after some other resource? How long is the wave of "shimmering" and how does it scare off the hornet? Good work.

-Carlos A. Varela


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