Hi:

Just because they are called queen excluders doesn't mean that these
devices exclude every queen. Plastic, wire, U.S., European excluders -
makes no difference, we find queens above them.  We've seen marked queens
go through them, both up and down, as if the excluder wasn't there.  You
don't have to blame all of this on bent wires, the beekeeper, or gremlins.
Remember, queens vary in size - excluders don't (although they do vary from
different manufacturers.  Queens also vary in behavior - some seem to be
very much inclined to crawl through excluders, same as some cross honey
arches and end up in the top box.  I've seen queens at the top of a 5 or 6
box stack, with brood in the bottom box or the second box, and fully drawn
frames in between, and she's up in the top, laying eggs.  And, she may have
recently laid eggs in both the top and bottom - so she didn't gradually
work her way up.

Excluders keep most queens where you want them to be.  Larger beekeepers
use them to reduce the need to inspect honey supers for brood - but some
get through and end up in the extracting room.  Depending on your locale,
both commercial and hobbiest beekeepers may put on excluders to limit the
queen's egg-laying.  If you have early season nectar flows and then not
much else, you may need to slow down the population growth - or else the
bees will consume most of what they stored.

Queen excluders may cause colonies to supercede queens - we've seen a lot
of this in large apiaries - especially if the excluders are put on at the
same time as extra empty supers during a heavy nectar flow.

Personally, if the area has adequate carrying capacity (reasonably diverse
and consistent nectar sources for most of the spring-summer-early fall, I
prefer to not use them.  Bottom line, they retard reproduction and
population growth - so keep that in mind.  That may be what you want/need
to do.

Cheers

Jerry





Jerry J. Bromenshenk
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http://www.umt.edu/biology/bees