Murray McGregor wrote:

> I should imagine that regular (both assisted and natural) incursions
> north of their line will take place every year, followed by dying back
> in the winter. (As an aside, migratory colonies could be well on their
> way back south before this phenomenon kicks in, possibly leaving genetic
> havoc in their wake amongst resident colonies in the north.)
-
> Murray McGregor

I have asked the same question of the experts when they visit Maine for our
Annual Meetings. Why is there a limit to the AHB migration in SA?

The answer is they do not know, but there are plenty of guesses.
The one that makes the most sense is the nature of AHB to abscond and swarm
often. The experts say that AHB casts off more swarms than EHB and absconds
more.

Picture that trait in a northern bee and it would have much less chance of
surviving the winter- less stores and possibly poor hive habitat. I know
that if a hive swarms in the fall in Maine, it has increased its chance of
winter failure greatly, usually to near 100% unless the beekeeper
intervenes.

It seems to also track with the fact that there is a transition zone in SA
where the AHB decreases as the EHB increases as you go south. Some AHB
would survive the winter, but in lesser numbers as it gets colder. EHB
survives in greater numbers as it gets colder so more EHB drones are
available to increase the likelihood of EHB dominance. This is in line with
Murrays guess of the ebb and flow with summer and winter.

As far as migratory beekeepers wrecking havoc, there were 60,000 migratory
hives in Maine this year which came from all over the South and West. Some
will eventually have AHB and swarm. If a beekeeper hives the swarm, I have
been told it will over winter just fine in Maine, if managed properly with
fall feeding.

But, the feral colonies it creates should meet the same fate as those in
SA, so I doubt if AHB will dominate in colder climates like Maine. Here EHB
would have the genetic advantage.

It will also be interesting to see what happens in that transition zone.
You will have AHBs advantage of earlier queen emergence against EHBs winter
tolerance. Where you have equal strengths, will EHB shift to earlier
emergence to compete, and will AHB shift to lees absconding and swarming?
It could be a geneticists dream to study the genetic warfare that will be
going on.

All guesses, but interesting.

Bill Truesdell