Quote  -  "When mites are not attached to a host the distance they will
travel is
limited. At EAS it was stated that the longest distance a Varroa would
travel was about 3/4 of an inch. If it does not find a host it stops and
waits, many times until it drys up and dies."

Not in my experience, have seen them rushing from one side of a frame to
another, and always been amazed at the speed they can travel. What I think
might have been suggested is the depth below the frame where they cannot or
will not climb back up, but I thought that was more than 3/4 of an inch.

Ken Hoare