447 



continuous loss of blood resulting from the feeding of the mite, Acarapis 

 [Tarsonemus) woodi. The blocking of the air tubes restricts the supply 

 of oxygen, and leads to considerable deterioration of various tissues, 

 this injury being of a secondary character. While many of the mites 

 remain within the tracheae of the bee, many females after fertiUsation 

 pass to the outside of the host, where they may easily be rubbed on to 

 other bees by contact, and this is probably the greatest source of 

 infection. These migrating females invariably find their wa}^ to one 

 of the first pair of thoracic spiracles, which they enter, and generally 

 begin to oviposit near the entrance to the tube, all stages subsequently 

 being found all along the tracheal system of that part of the body, as 

 far as the diameter of the tube will allow the mites to pass. Evidence 

 all tends to show that the disease is almost entirely a contagious one, 

 carried by the living bee. The crawling symptoms in acarine disease 

 are periodic, especially in summer, while new bees are being produced 

 in large numbers, for although a proportion of these may become 

 infected early in their adult life, they continue to fly and work for a 

 considerable time. During this time crawling may be practically 

 absent, and a false impression of recovery from the disease is often 

 conveyed. The saving of the queens of affected stocks is not recom- 

 mended, as a large percentage of them is often found to be infested with 

 the parasite. 



Only adult bees have been found to be infested, and it has been 

 noticed that the note emitted in flight by an infested worker differs 

 from the normal, resembling rather that of the drone. The disease ma}^ 

 sometimes be detected by this means. The main contributing factors 

 affecting the course of the disease are discussed, such as the importance 

 of a good queen, the advantage of numerous workers, etc. Regarding 

 what has been said and written of races of bees immune from acarine 

 disease, the author does not admit that there is any evidence that such 

 a race exists, nor does he think that any race would be immune unless 

 . one could be bred with spiracles too small to admit the mite to the 

 respiratory system ; he suggests that the production of vigorous and 

 fertile races is the best antidote to acarine infection. 



A. li'oodi breeds all the year round, and infective migrations from 

 bee to bee are continuous throughout the year. Winter is, however, 

 a critical period, all the circumstances favouring a steady increase of 

 the disease, and either the stock will not survive the winter, or it will 

 survive with a high proportion of infected and weakened bees. This 

 mortality is somewhat counteracted by the fact that the normal 

 longevity of the bee is much greater in winter than in summer. 

 Beekeepers are urged to estimate carefully the prospects and general 

 risks before deciding to spend time and money in feeding a colony 

 up for the winter, and the keeping of winter stocks known to be diseased 

 is deprecated. 



Besides the method of infection described above, there are numerous 

 outside sources of infection, such as robber bees, drones, drifting bees, 

 or casual individuals entering a wrong hive. By these means, especially 

 if they occur together, the disease may reach a critical stage very 

 quickly and in a large number of bees at the same time, and crawling 

 may be sudden and extensive. Mass crawling is also brought about 

 sometimes by the swarming of bees already weakened by disease. 

 When large numbers are known to be crawling in the immediate 

 vicinity of healthy stocks, the presence of a few crawler traps in the 

 apiary is recommended, until the cause of the crawHng is ascertained. 

 If it is known to be due to acarine infection, grass harbouring crawling 



