APPENDIX. 



ON THE ACAEINB DISEASE OF HIVE BEES. 



SUB-ORDER HETEROSTIGMATA. 

 FAMILY TARSONEMIDAE. 



Genus Acarapis, Hirst, 1921. 



The genus Acarapis is closely allied to Tarsonemus, from which 

 it differs as follows : Second and third legs of larval stage very 

 short (almost rudimentary) and without either claws or sucker 

 (figs. 82 and 83 c), whereas, in the larva of Tarsonemus, these legs are 

 about as long as the first and are provided with paired claws and 

 a sucker (fig. 84). 



The female of Acarapis lacks the club-shaped pseudostig- 

 mata present between the first two pairs of legs in that sex in 

 Tarsonemus, and the fourth leg is shorter and wider, being provided 

 with more numerous hairs (in this last respect somewhat resembling 

 the fourth leg of Scutacarus). 



Acarapis woodi, Rennie, 1921. 



(Figs. 78-83.) 



For a longtime the " Isle of Wight Disease " of bees was thought 

 to be due to a protozoon parasite (Nosema apis). But Rennie, 

 White, and Miss Harvey (Trans. Roy. Soc. Edinburgh, LIL, 1921 , 

 pp. 737-779) have found a Tarsonemid mite constantly present in 

 the thoracic tracheal tubes of bees suffering from -this disease. 

 Loss of the power of flight is one of the chief distinguishing features 

 of " Isle of Wight " Bee Disease, and another is the great mortality 

 that occurs amongst infected bees. " Crawling " bees are usually 

 present in numbers in diseased stocks. According to Rennie crawl- 

 ing appears to be intermittent. Apparently on very warm days an 

 excessive amount of crawling may occur, ridding the hive of the 

 bulk of the heavily infected individuals and lowering the proportion 

 of sick bees in the hive. New bees are being produced in large 

 numbers at certain times of the year, and even if some of them become 

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