Does anyone know what units pheromone is expressed in? For example, we often say that younger queens have stronger pheromone than older queens; is this in ppm or some other units? As well, what type of volumes correspond to these units, ie. 50ppm vs 500ppm?
Yes, one could take a sample of air and run it
through a gas chromatograph or HPLC/MS, and
measure the relative amounts per unit volume of
air, which works out to parts per million,
billion, maybe even trillion.
Pheromones are "volatile organic compounds", so
they would be tricky to measure. You'd likely
need portable gear, or need to bring the queen
to the gear.
But some pheromones from the queen don't work as
a "scent in the air". The pheromones that keep
workers from developing ovaries, and perhaps other
specific pheromones, were found to be transmitted
by touch (workers licking the queen, touching,
etc) those bees then spread the pheromone by
contact to other bees.
There are several good (but highly technical)
books on pheromones out there, perhaps the
best being "Pheromones of Social Bees" by
John B. Free.
About the best estimates of the minimum pheromone
levels required to "work" have been arrived at by
taking synthetic analogs to the various
pheromones, and either touching them directly to
workers who don't have a queen, or letting a
volume of the chemicals act as an "air freshener"
for a group of test bees.
If the pheromone "works", you have "enough".
If not, you may need more, or you may not have
provided the correct MIX of the different known
pheromones. (Often it takes multiple pheromones
to get the detectable behavior one is looking for.)
I don't know if anyone has done the work to come
up with either measurements from queens directly,
or a calculation based upon the amounts of
pheromone one must "apply" to get a detectable
response for this or that, but I do know that
the bees are quite emphatic about older queens. [img]smile.gif[/img]