Dance language enthusiasts have published a "Letter to Nature"
- "Honeybee dances communicate distances measured by optic flow",
Esch et al. Nature, vol. 411, 581-3, 31 May 2001 - which lacks
controls and statistical treatment. I have attached a copy of
the abstract of the paper below.
If one reads the paper carefully, a couple of points emerge.
One is that the researchers have used an unexpected result
(that in the experiment done in the northwestern direction),
not to question the whole von Frisch hypothesis, but to support
their NEW version of the hypothesis. They are claiming that
"optic flow" is the important feature of a bee's trip, in
contrast to earlier claims that energy expended is crucial,
and the original claims that distance information is objectively
accurate. In short - the hypothesis keeps changing.
Their claim that the difference in the waggle duration between
the two geographic directions is due to differences in the
optic flow is simply asserted. No evidence is provided, other
than vague descriptions of the topography.
Another point is that the actual results are not that impressive.
For example, in the third experiment, as many bees go to one of
the "wrong" sites as to the "right" one.
It seems a particular weakness to me that there were no control
sites in directions other than what the researchers expected.
Wenner has noted that bees searching for food fly out of the hive
in "ever-increasing spirals". This suggests that they will
therefore encounter observation sites set up in ANY direction.
Esch et al. remark "Recruits searched for a short time [at the
observation sites] and disappeared". I'll bet they did - they
were probably just randomly buzzing around!
What Esch et al. (2001) represents is another in a long line of
inconclusive experiments designed to prove that honeybees have
a language.
There are possible explanations for the evolution of the honeybee
dance that do not involve directional and distance communication.
I have given one at:
http://naturalscience.com/ns/articles/01-13/ns_jdo.html
No doubt there are others.
Julian O'Dea
Canberra, Australia
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Honeybee dances communicate
distances measured by optic Ųow
Harald E. Esch*, Shaowu Zhang², Mandyan V. Srinivasan²
& Juergen Tautz³
* Department of Biological Sciences, University of Notre Dame, Notre Dame,
Indiana 46556, USA
² Centre for Visual Science, Research School of Biological Sciences,
Australian National University, Canberra, ACT 2601, Australia
³ Biozentrum Universita»t Wu»rzburg, Am Hubland, D-97074 Wu»rzburg,
Germany
..............
In honeybees, employed foragers recruit unemployed hive mates
to food sources by dances from which a human observer can read
the distance and direction of the food source1. When foragers
collect food in a short, narrow tunnel, they dance as if the food
source were much farther away. Dancers gauge distance by retinal
image flow on the way to their destination. Their visually driven
odometer misreads distance because the close tunnel walls
increase optic flow. We examined how hive mates interpret
these dances. Here we show that recruited bees search outside
in the direction of the tunnel at exaggerated distances and not
inside the tunnel where the foragers come from. Thus, dances
must convey information about the direction of the food source
and the total amount of image motion en route to the food source,
but they do not convey information about absolute distances.We
also found that perceived distances on various outdoor routes
from the same hive could be considerably different. Navigational
errors are avoided as recruits and dancers tend to fly in the same
direction. Reported racial differences in honeybee dances could
have arisen merely from differences in the environments in which
these bees flew.
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