In message <[log in to unmask]>, Robert Brenchley <[log in to unmask]> writes ><<The darker bees from northern Europe generally are more resistant to >tracheal mites. >> > > If this is the case, why was A. mellifera mellifera in Britain so >susceptible in 1920? There are many myths in beekeeping and this was one. Read Beowulf Cooper's The Honeybees of the British Isles BIBBA 1986 for a summary of his findings. From memory it was more the crosses with Italians and the Italians which were susceptible to the IOW disease. The native dark bee is alive and well, though mongrelised somewhat, except where natural selection kept it going (before varroa). For example in Scotland, Murray MacGregor's Carniolan crosses which hew uses in his migratory setup revert over the years to native and he introduces new Carniolans. Here in West Cornwall we have little sign of acarine damage. Nosema is more obvious and a new pocket of European Foul brood is proving difficult to eradicate. Brother Adam is one of the main proponents of the "native bee is dead" myth. The IOW disease turns out to be one of the viruses which are propagated rather well by varroa, I think it is now thought to be the Slow Paralysis Virus which caused it. Acarine may well have been the stimulus. -- James Kilty