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Dear Kenna:
           Your query about hole-biting in highbush blueberries seems to
have caught us all off guard:  I, for one, did not know before I read
your message that anybody grew highbush blueberries in Nova Scotia!
  On the whole, I would put my money on Bombus terricola as the source
of your holes.  It, together with affinis and occidentalis (and a few
other minor species), are members of the subgenus Bombus sensu stricto,
and all of them (as with the European members of the same subgenus) are
enthusiastic hole-biters.  They even have specially "notched" mandibles
which have been considered adaptations for this same purpose.  I don't
have records that B. affinis occurs in your newly adopted province (and
occidentalis is purely a western species), but terricola is common as
the proverbial merde . . .
  We watched, in Michigan, both B. affinis and Xylocopa virginica (or
should it be "virginiana"? please forgive my sloppy taxonomy) biting
holes on the highbush blueberry variety "Jersey" this spring.  Kristy
Ciruna, one of the members of our field team, recorded that the bees
gave a distinctive "crunching" sound when they were carrying out their
evil deeds.  I will ask Kristy when I next see her (she is currently
working on lowbush blueberry pollination near Lac-St-Jean) whether the
holes that affinis bites resemble the slits produced by Xylocopa.
  The ecological and economic significance of hole-biting on blueberries
is a matter of debate: on the one hand, it is certainly the case that
honeybees use the slits to "rob" nectar from the flower, but on the
other, pollen-collecting bees (which, from our results this spring seem
to be doing about 99% of the pollination) usually ignore the holes
entirely.  Also, it must be remembered that female Xylocopa (and bumble
bees too, of course) are highly effective pollen foragers on blueberr-
ies--so along the lines of my previous sentence, it may be that their
pollination more than compensates for any indirect effect that they have
on honeybees.  I'm sure that we will have this information within the
next year or two.
  More subtle is the effect which hole-biting may (possibly) have on the
working speed of legitimate pollinators: in rabbiteye blueberries espec-
ially, the working speed of bumble bees is sometimes extremely slow
because of the fact that nectar accumulates in prodigious amounts within
the flowers (honeybees can't easily reach withing the corrolae of some
rabbiteye cultivars), so they sit for quite a while gorging themselves
on each flower.  So, the argument goes (and it isn't mine, I may say),
if the honeybees are able to use the slits made by the Xylocopas to
lower the average amount of nectar in the flowers, then the bumble bees
will work faster and pollinate more flowers!!  Unfortunately, it is
quite likely that this argument is really a pile of the aforementioned
merde, because we are beginning to find more and more that the only
really effective pollinators on Vaccinium are those which are actually
foraging for pollen: and these, as indicated earlier, don't seem to take
much notice of the holes . . .
  I hope that I have written enough to convey to you my enthusiasm on
the subject of hole-biting.  Certainly, as first-year graduate students
are wont to write at the end of their first manuscript submitted for
publication: "Much more research needs to be done in this fascinating
area!".  Now if only those who hold the purse-strings would get the
message . . .
  Best regards, Chris Plowright.
 
--
Chris Plowright - via the University of Ottawa
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