Well...short answer, they don't always get it right, but they are close
usually.
The timing for when the swarm goes is not be exact to one day, and that's
why sometimes you see them abort because the queen is not quite ready, even
if everything else is go-go-go; and sometimes the hives all go swarming mad
on the next available sunny still day as they have been ready for a few
days just waiting on the weather.
So, more about timing - the swarm doesn't leave the hive until they have
got capped princesses. These are capped 8 days after being laid, so you are
essentially asking not "how do they know 3 days in advance" but "how do
they know 8 days in advance?" Answer: they don't. They take their best
guess, and sometimes they get it wrong (we sometimes have to rescue swarms
which called the weather wrong and got caught out by rain after leaving the
hive). Sometimes the prime swarm is delayed by poor weather for over a week
and then virtually overlaps with the casts headed by princesses - really
mad swarmy days.
They have evolved mechanisms for handling "schedule slippage" precisely
because they DO get it a bit wrong sometimes. It's known the workers can
keep the princesses capped longer than the 8 days they need to mature, like
a "princess bank", and use them as insurance in case the first princess
doesn't come back from her mating flight. They can also herd the queen away
from them, and stop hatched princesses killing the others.
But in general -
- The colony begins preparations by creating queen cups first, then when
they detect good local conditions they get her majesty to lay eggs, These
conditions are when their numbers / stores / forage are good, or to put it
another way when the forage is in full flow and they feel their colony is
'secure'.
- This is why you always want local bees, they are well adapted to their
area - they are already programmed to the local forage rhythms (1).
- They can also sense air pressure, so can probably tell "the weather
has been warm and settled for a few days" and so swarming weather is likely
to be in the offing, But like weather forecasters everywhere, they
sometimes get caught out. And then have to manage accordingly.
Paul & Lynne
(1) Presumably bees in very different areas to ours, like heather moors,
swarm in e.g. August because that is when the long heather flow is
maximised. Anyone know for sure?
On Mon, 2 May 2022 at 14:40, Barbara Elizabeth Robinson <liz20swan@xxxxxxxxx>
wrote:
Hi all. So I am just trying to explain about swarming to someone good at
asking tricky questions!
I understand that the old queen is not fed for 3 days prior to swarming to
enable her to be light enough to fly. How do the bees know that in 3 days
time the weather will suit swarming? So my bees swarmed on Saturday which
was perfect swarm weather. Are the bees that good that they predicted the
fine weather 3 days hence? Would they have swarmed if it was cold and wet?
I think not.
Any help would be appreciated.
Liz.
