Minimum size opening for a mouse to slip through needs qualifcation; while it is true that they can slip through a slot as narrow as a quarter of an inch, the minimum diameter of a round hole is about half an inch.  A square hole has a bit different limitations in that its diagonal measure is ~ 5/8".  Shrews can be considerably smaller than mice but their bone structure is a bit different.  1/4" mesh keeps both out but easily plugged with dead bees or uncooperative drones being evicted. Too bad 3/8 mesh screen was not more commonly available.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html