I have been corresponding with two neuroscientists about the bee brain.  I
would like to forward this letter to the list because some may enjoy it, and
I will add some comments to the end.
 
>Stan:
>
>I have found a good reference with some numbers concerning the brain of
>the honey bee.  The reference:
>
>Peter G. Mobbs, "Brain Structure" in Comprehensive Insect Physiology,
>Biochemistry and Pharmacology, edited by G.A. Kerkut and L.I. Gilbert,
>Oxford: Pergamon Press, 1985.
>
>Some of the numbers (Apis mellifera)
>
>                       Worker          Drone
>                       ------          -----
>Total Brain Volume     1.321 mm^3      7.839 mm^3
>Total # of neurons     851,458         1,209,681
>
>Note that these volumes include the suboesophageal ganglion.  There are
>also numbers for mushroom bodies, central body, protocerebral
>bridge, optic lobes and antennal lobes (all volumes).  Figures allow for
>shrinkage during processing.
>
>I was surprised at the difference between the drone and the worker bee and
>also of the relative small number of neurons in the drone given the much
>large brain volume.
>
>Eric
>
>Eric H. Chudler, Ph.D.
>(E-mail: [log in to unmask])
>(URL:   http://weber.u.washington.edu/~chudler/neurok.html)
>(URL:   http://weber.u.washington.edu/~chudler/ehc.html)
 
First, I would like to mention that Dr. Chudler's web pages are well known
as being a first rate neuroscience web site.  There is little there about
insect neurophysiology right now, but he is working on it!
 
What follows is pasted from my reply to him, and he is not a beekeeper or
entomologist so please forgive me for restating what is obvious to you:
 
Drones differ from workers and queens in that they are genetically haploid.
 
  "The drone has a short tongue, which he uses to take food from workers and
from honey-storage cells in the hive; he does not collect food from flowers.
He has neither pollen baskets nor wax-secreting nor scent-producing glands.
So far as is known the drone does no work in the hive, his only function in
life being to seek a nubile queen outside the hive and forfeit his life
mating with her".
 
Drone's also are notoriously poor at reorienting to their home hive, which
workers do with a combination of visual (colour and shape), olfactory, and
landmark cues.  They often drift.
 
But, to do their job they are strong flyers and have a good sense of smell
(they home on queen pheromone).  There are about 30,000 plate organs on the
drone's antennae compared with 5-6,000 on a worker's and 2-3,000 on a
queen's.  Sexual selection often produces dimorphism in mammals (big bull
walruses, etc.) and if it has tended towards a bigger drone then perhaps
most of the brain volume, except for the olfactory lobes, is superfluous.
With an animal that has invested 5% in brain volume one would expect
superfluous neurons to be limited.  In fact, I linked from your pages to an
article on neuron death which was exploring strategies for limiting
superfluous neurons (THE CONTROL OF NEURON NUMBER,  Williams and Herrup,
Ann. Rev. Neurosci,  1988,  11: 423-453).  The article concentrated on
neuron production, and TIME of production, and neuron death.
 
Considered the few instinctive behaviours that drones are programmed for
compared with the multitude in the worker the fact that the brain is bigger
at all is surprising and maybe is just due to having to fill up the bigger
brain cavity, so to speak, and thus the smaller relative neuron number is
not nearly so surprising to me (although I qualify this in that I will be
curious to see what proportion of the brain volume is in the olfactory
lobe).  I have found a reasonably good diagram of the parts of the bees
brain and ganglia system so I should be able to follow the table.
 <end of paste from reply>
 
There seems to be a scarcity of females in this group, or at least in the
postings (are women quieter :)   But if I was was a female, or a feminist, I
think I could find some ammunition here against the argument that some
(probably only those who enjoy sleeping in the honeyhouse) might make that
the male brain is bigger.  (See  ..../~chudler/heshe.html)   The larger
brain in drones is certainly not accompanied by greater capabilities.  It is
over four times the size but has only 50% more neurons.  Drones are empty
headed so to speak.  It is not how big it is that is important, it is how
you use it.
 
In SMALL but PRODUCTIVE Prince Edward Island
Stan
 
P.S. Today (Friday 13) is I believe the day of the patron saint of
beekeeping.  CBC radio will be celebrating it on Richardson's Roundup in
lieu of Valentine's day (since that is on a Saturday and the show is only
weekdays).  Show airs 2-4 pm here.  Honey is better than chocolate.