A very interesting story Jerry!
>Years ago, we used a front entrance pollen trap that proved to us just
>how variable body size was.  We ended up using two traps, fitting the
>traps to the size of the bees.  Curiously, last summer, bees that fit
>through a plastic pollen grid in Montana couldn't get through the same
>grids 4 days later after moving them to Maryland.
 
I certainly wouldn't even venture a guess as to the effect of elevation!
As far as the normal size variation requiring two trap sizes:
Were the bees on different types of comb?  That is, do you attribute the
size variation to the fact that some were on old comb with smaller cells, or
to genetic variation?  Also, where can one obtain plastic pollen grids; I
use square mesh hardware screen (5 X 5 mesh) doubled, i.e. one on either
side of the masonite slider.  Do the plastic pollen grids have round holes?
Do enough bees go through with intact loads to maintain brood rearing, or
are you using them for experiments where you want to weigh almost all the
pollen being brought in.
Thankyou,   Stan