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ACAllINE DISEASE EXPLAINED. 

 By JOHN RENNIE, D.Sc. 



I.— INTRODUCTORY. 



In Acarine Disease the thoracic breathing tubes of the 

 Hive Bee are infested with mites, which pass through 

 the whole of their growth stages from egg to adult in 

 this situation. The mites are true parasites, members 

 of the Family Tarsonemidae. All types of adult bees are 

 liable to be affected — worker, drone and queen. The 

 mites feed, breathe and breed in the region indicated, and 

 the result of their secure establishment is the eventual 

 disablement of the affected bees. This is primarily due 

 to a continuous loss of blood, on which the mites feed. 

 The degree of blocking of the air tubes, restricting 

 the supply of oxygen and causing a deterioration 

 of tissues directly connected with these, varies con- 

 siderably. This is a secondary complication. Weak- 

 ened bees may continue working for a long time, but 

 eventually they become unable to fly and cease to 

 share in the co-operative activity of the colony. They 

 thus become not only useless members, but a burden 

 upon their fellows in the hive. Such bees — popularly 

 termed " crawlers " — while remaining associated with 

 the stock are a continual source of danger to the healthy 

 brood which is successively emerging from the cells. 



As indicated above, this is a disease of the adult bee. 

 Practically the only chance of brood becoming infested 

 with Tarsonemus lies in the possibility of migrating 

 females wandering upon the larvae within the cells and 

 entering their thoracic spiracles. We have no clear 

 evidence that this ever takes place. Such behaviour 

 is probably not in accordance with the normal instinct 

 of the mite. Experiments in which frames of brood 

 from diseased stocks were transferred to healthy stocks 

 failed to produce the disease. Such brood in healthy 

 surroundings, easily traced, e.g., when brood of an 

 Italian queen is placed in a hive of ordinary black bees 

 or vice versa, remains free from Tarsonemus infestation. 



