In a message dated 16/01/03 05:03:47 GMT Standard Time,
[log in to unmask] writes:

<< Tracheal mites continue to be a problem. It depends on where you are
 located.  Colonies with high infestations in the south do not suffer from
colony
 mortality by tracheal mites. Colonies with similar high infestations in
 the north experience high winter mortality.  >>

Could it be that in the south there are more days of flying weather and crops
to fly to?  Adult infested bees are then more likely to spend more time in
the field and die there, spending less time rubbing shoulders with vulnerable
youngsters in the hive than those in less favoured areas.

Chris