Subject: Swarming after a thunderstorm?

From: [email-masked] (jim stevens)
Date: Mon, 09 Dec 1996 19:57:58 GMT

Hi

	My girlfriend is helping produce a play in Sydney called the Herbal
Bed.  It is set in Stratford, England where it has been very hot and
dry for 8 days.  Two of the lines are:-

"the bees didn't swarm then?"

"no, we need a good thunderstorm to get them stirring"

 She would like to know 
	  i) why they want the bees to swarm?
	 ii) would they not swarm in hot/dry weather?
	iii) why would a thunderstorm make them swarm?

  Thank you for any help

Jim Stevens 
(for Jane FitzGerald - [email-masked])

---

From: [email-masked] (Joel Govostes)
Date: Wed, 11 Dec 1996 14:23:18 -0500

>         iii) why would a thunderstorm make them swarm?

Hi Jim,

i)  Swarming is the natural division of a colony, when a large portion of
the population (tens of thousands of bees) just flies out and away, with a
queen, to found a new colony elswhere.  The swarm usually clusters
together for a while in a big bunch, on a tree limb or something, and at
that stage a beekeeper can shake  or brush them into a new hive, which
they will eagerly enter, to set up housekeeping.  Otherwise, they will
find some hollow tree or other cavity to use, and will move into that.  

i) "In olden times," people wanted the bees to swarm, so they could catch
the swarm and hive it, increasing their number of hives.  That was the
only way they knew how to start new or additional colonies.  They wanted
as many colonies as they could get, as honey was their precious
sweetener.  

ii)  Swarming usually takes place in mid-late spring. For a number of days
prior to the swarm's issue, the bees' activities slow way down and they
start "hanging around" the hive.  They aren't so busy, almost like they're
on strike.  Sometimes you can see hives almost completely covered with
bees on the outside, as they await the proper time to "take off."  Very
hot or dry weather (or both) would tend to postpone the issue of the
swarm, as after several dry hot days, the flowers' nectaries would largely
be dry.  They wouldn't be producing much nectar, and so the food supply
coming into the colony would be low.  This is like taking the fuel away
>from  a fire -- it starts burning down slowly.  It is also more difficult
for insects to survive in very hot, dry weather, as their bodies can dry
out quickly (high surface/volume ratio.) With the sudden arrival of a
thunderstorm, the atmostphere changes quickly and moisture is everywhere.
 This abrupt change is often an impetus for immediate swarming.

As an example, I remember late one June afternoon after a sudden strong
thunderstorm, I happened to be driving by one of my bee locations, and
decided to take a quick look at their activity.  It was late in the day,
perhaps 4:30.  My pants legs became soaked as I trudged through the tall
grass, wet with rain.  The storm had moved away and the sun was blazing
brightly.  As I approached the clearing, I could hear a great rushing
sound.  At once I was greeted by the sight of a large airborne swarm
gleaming in the sunlight, settling down to one of my empty hives.  They
converged on it for a number of minutes, and gradually entered, "claiming"
their new home.  It was a remarkable sight.  I was amazed that they had
migrated to the empty hive (from who-knows-where) so late in the day, and
especially after such a thunderstorm! (It was much later in the day than
the time when swarms usually migrate, between 10 am and about 2 pm.)

iii) Bees are affected by barometric pressure.  High humidity and heat can
drive much of the population to the outside of the hive, as mentioned
above.  They need to allow space for air to enter and pass thru the hive,
to keep it from overheating.  With the advent of a thunderstorm you have a
sudden, major change in the pressure, temperature, and humidity.  This
serves to push the bees over the edge, and the swarm comes forth.  Exactly
why, I am not certain.  I mean, I don't know if it is the humidity,
pressure, or rain,  or some combination, but there is a definite
correlation, and after all, yes, thunderstorms do often "trigger"
swarming.  They are not a prerequisite, tho'.  Maybe someone else can
supply some more details. 

All I know is that in early June, if there is a good week or two of
increasingly hot, humid weather, followed by a cold front brought on with
a line of thunderstorms, that is the most likely time for swarms to
issue.  No doubt about that.  I hope this information is helpful.   BTW I
am in central New York State.  Our late spring/early summer weather
patterns are usually like I just described.  High pressure systems move
across the USA  and eventually things start heating up.  It can get
downright muggy and hot for days at a time.  Then suddenly a cold air mass
or low pressure system will drop out of Canada, setting up frontal
zones and huge lines of thunderstorms.  It is one of the interesting
aspects of living here in the Northeast.  Best wishes, JG