Alan Sharratt asks about tracheal mite, its recognition and control in NW UK.
This is largely a pest of the past at least as far as southern England is
concerned.  Where it does flare up it is usually in colonies with imported
queens.  Alan will be lucky (or unlucky!) if he find it.  We have difficulty
in finding affected hives for beginners to practice recognition through
dissection.
UK publications do not refer to it as tracheal mite but as Acarine.  There is
no legal chemical treatment in the UK at the moment.  If it is found and if it
is a real problem rather than just a curiosity I would suggest requeening with
a queen obtained from a successful local beekeeper whose bees don't have
Acarine.
 Dr. Bailey suggests persuasively that the mite multiplies more rapidly and
becomes a nuisance when an area is over-stocked with bees.  My (fallible)
memory tells me that an average local density greater than 1 hive per square
kilometre, if that square kilometre has a reasonable amount of forage, is over
stocking.  Perhaps it is more of a problem in America because for economic
reasons professional beekeepers keep a large number of hives in a small area.
Chris Slade