According to Page & Laidlaw and Sue Cobey the tendency to swarm is
definitely controlled by genetic factors.  Moreover, it is one of those
factors that is relatively easy to select for (or against) and to control in
a given population.

While it may be possible to select for bees that will not swarm, I do not
believe breeders are attempting to do so.  Instead, they are selecting for
strains that will not swarm if given enough room.  Of course, "enough room"
is a subjective measurement, but if all colonies have the same amount of
brood and super space and some swarm and others do not, those that do not
may be termed as having a reduced swarming tendency.

I have been following the swarming thread with interest.  Personally, I do
not believe that using swarm cells necessarily means that one is selecting
for swarming.  There are too many other variables to consider.  A couple of
those are, how much room was available? And what was the age of the queen?
Certainly I would not want to use swarm cells from a current year queen, now
would I want to use swarm cells from a hive that has three empty deeps as
supers.  Those examples, of course, are extremes.

On the other hand, if I had a yard where virtually all my hives were
preparing to swarm (due to lack of room) I would not hesitate to use swarm
cells from any one of those hives.  Unfortunately, I have had just that
experience.

Lloyd
Lloyd Spear Owner, Ross Rounds(tm).  The finest in comb honey production.
http://www.rossrounds.com