243 



The actual facts are as follows : The origin of the 

 swarm infestation and that of the primary stock is 

 one. It may be due to any of the several causes 

 already suggested. Where the proportion of affected 

 bees is very high the infestation may date from the 

 previous autumn or to early summer robbing of weak 

 infested stocks. The older bees constituting the bulk 

 of the swarm are in a. more advanced stage of infestation 

 than the younger, who largely make up the remaining 

 colony. But whilst this may explain the earlier onset 

 of crawling, it does not explain its association in mass 

 with the event of swarming. 



The mass crawling in this ca-se is really a premature 

 collapse brought about by the excitem,ent of swarming 

 in bees already weakened by disease. Crawling here 

 cannot be associated with a critical position of the mites 

 in the tracheal system both on account of its sudden 

 and general distribution and of the varying degrees 

 and position of the infestation actually present in the 

 bees concerned. 



Sometimes the crawling does not take place immedi- 

 ately after swarming, but may be delayed. On the 

 other hand, I have witnessed its onset during the 

 swarming, when the vast majority of the flying swarm- 

 ing bees came to the ground not far from the parent 

 hive and never rose again, whilst others issuing, crawled 

 around the doorway and upon the hive. 



Periodicity of Craivling Symptoms in Acaiine Disease. 



It is a matter of common observation, more particu- 

 larly in summer, that there are intermittent periods of 

 crawling in Acarine disease. This feature is readily 

 understood when we realise that an excessive amount 

 of crawling, such as is seen to occur frequently on very 

 warm days, rids the hive of the great bulk of individuals 

 in the advanced stages of infestation, and in this way 

 lowers the proportion of infested individuals in the bee 

 population. Whilst this is going on new bees are being 

 produced in large numbers, and even although a pro- 

 portion of them may become infested quite early in their 

 adult life, they continue to fly and work for a consider- 

 able period. There is no doubt that this is so. Thus 



