I must assume that one of the main reasons for my colony losses must be queen failure, and the reason for this is another six-marker. We never had a problem with queen failure until the arrival of varroa. It may be due to the scarcity of drones, as not only the drones themselves but the gene pool has been has been greatly reduced by the decimation of all the wild colonies, as well as the many extra colonies that were kept by let-alone beekeepers. Perhaps the chemical treatment that we are using for the control of varroa is also having a bad effect on the viability of drones or even the queens. Even though Bayvarol is not applied during the queen- or drone-rearing season, it is possible that residues of the chemical remaining in the comb may affect queens and drones. It may be a good idea to use an alternative treatment in the breeding apiaries in future. So far in this country, it is possible to keep down the level of mites through appropriate treatment with acaricides. However the effects of varroa-associated viruses are very difficult to quantify or understand. Even the research teams working on them seem to have difficulty in identifying their damage, let alone coming up with some measure of treatment or prevention of the damage caused by them. Only on rare occasions do I see a bee with deformed wings or stunted abdomen, but it seems that this virus can be present in workers, queens and drones, and there are no apparent symptoms. Research work has proved that this virus can be transmitted from the drones to the queens during the mating process. The presence of this virus may affect drone fertility and may seriously interfere with the egg-laying ability of queens. This may be one of the reasons why so many queens are being superseded at an early stage in their productive life. When this supersedure occurs very late in the year, there is little chance that the resultant queen will be successfully mated.