Last week someone mentioned that it could be the size of the cell and
pressure on the abdomen that causes the queen to fertilize or not fertilize
the egg.  This fired a few synapses and I went back and reread Hubers 8th
letter.  In this experiment he only allowed the queen to have drone size
comb, she was initially quite confused by this but eventually laid
fertilized eggs, albeit in may cases she laid multiple eggs per cell.  This
observation would seem to belie the theory of pressure causing the
spermateca to release sperm.

Dave