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Dear David:
Thanks for your gracious reply to my snotty message (and
thanks also to Stephen J Clark and Barbara Thomson for their chidings--
there is nothing more powerful, in terms of immediate behaviour-modific-
ation, than being told off in public by the much-admired wife of a
former--and also much-admired--post-doc!). And, of course, you are
quite right when you point out that colonies of high altitude bumblebees
(and, indeed, those in high latitudes as well) are generally smaller,
and less rich in resources, than those in more lowland regions. But
even in the Colorado Rockies, you might be surprised--as I was when I
worked on Pennsylvania Mountain as a guest of Peter Kevan in 1980--to
discover how very opulent some high-altitude Bombus colonies can become.
I well remember "finding" (you could scarcely overlook them, given their
location) three bumblebee nests in a pile of old hives left by the late
(and much missed) Peggy Byron. Two were Alpinobombus nests (kirbyellus
or balteatus--whatever they like to call it/them these days) and were
the classically feeble little colonies that are characteristic of this
group of bumbles. They DID, I was glad to see, produce workers in their
second broods (the Arctic Alpinobombus--in contrast to those in the
Rocky Mountain Alpine--usually move directly to sexual production after
a single brood of workers), but neither could, as you say, have stored
more than a few grams of honey. But the third colony (of B. occidental-
is) was quite different: it became fairly monstrous (although nothing
like as large as colonies of that species on the west coast) and, at its
zenith, had accumulated substantial amounts of stored honey and pollen.
Another species that can sometimes produce quite large colonies in the
Colorado Rockies (i.e. over 100 workers) is B. bifarius--although most
bifarius colonies seem to be of only modest size.
The largest bumblebee colony (apart from the miserably enormous B.
atratus colonies that we kept in our lab in the late 1970's) that I have
ever had in my care was a monstrous B. impatiens colony that I allowed
to forage out of the window of my living room in 1991. This hive
produced something over 400 workers (we were never patient--or bold--
enough to count them exactly) and, after all the "hive-extenders" (the
equivalent of honeybee "supers") were added, occupied a space of 8" x 8"
x 24" (certainly nothing to write home about in honeybee terms, but
quite a commodious living space for a bunch of humble-bumbles). At one
point in the summer, it was necessary for us to move this monster: and
it was at then that the sheer weight of the edifice (mostly, we assumed,
the result of all the stored honey within the comb) was such a surprise
to us.
The other thing to remember in all of this is the incredibly skewed
frequency distribution of the sizes of bumblebee colonies: a small
fraction of the hives in a population "make it real big"--but the
majority never amount to much more than becoming the producers of a few
measly drones. There are parallels here, it would seem, with frequency
distributions of some economic enterprises (yes, I AM thinking of
McDonald's!), and although I'm not sure what Ed Wilson's current
thinking on these matters is, I can't help wondering whether the huge
(albeit rare) genetic payoff to the few "elite mega-colonies", with all
their wonderful economies of scale and superior competitive ability, may
not have provided a powerful selective force in shaping the evolution of
sociality in Bombus. Certainly, in the spirit of exceptions that prove
the rule, we may have something valuable to learn from your high-altit-
ude bumblewimps!
Best regards, and apologies for sniping at you, Chris.
P.S. I can't resist adding that I have forwarded the name of S J Clark
to the Provost as a candidate for the position of Dean of Sanctimony!
--
Chris Plowright - from "The Bumble Bee's Nest" at University of Toronto
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