56 Bee Disease 



slow and sluggish, may run rapidly, may tremble, present a hairless appear- 

 ance, drag its hind pair of legs helplessly, may be subject to dysenteric dis- 

 charges, or may impart a yellow colour to the interior of the hive by passing 

 constantly a tiny threadlet of faeces. Possibly the varying manifestation may 

 be due to the multiplication of bacteria of different species or of other parasites 

 in the bowel of the affected bee. Whether the condition is sometimes due to 

 infection it is impossible to decide. 



Again, the normal hfe of the individual bee may vary from eight weeks to 

 as many months according to the activities of the colony, and it may be that 

 organisms which do httle harm in two months cause serious trouble where the 

 necessities of the colony require the extension of the hves of its individual 

 members for a longer period. 



The difficulty of tracing a connection between a disease and any parasitic 

 organism that may be found in the bee becomes very real when the investiga- 

 tion of disease is attempted. If, while the external conditions are favourable, 

 the organism is fed to a colony as an experiment, the bees may fail to die or 

 to develop symptoms ; while if unfavourable conditions prevail at the time of 

 the experiment, death may be due to unrecognised causes, such as infection 

 with N. apis (see below). Apparently healthy bees, if prevented from flying, 

 will sometimes develop symptoms (crawling with bowel distention) indistin- 

 guishable from Isle of Wight disease. 



IV. Attempts to ascertain the Cause of Isle op Wight Disease. 

 A. Bacillus fesfiformis apis. 



The first to associate a definite causal organism with Isle of Wight disease 

 was the late Dr Walter Maiden (1909). He found no macroscopic appearances 

 in the diseased bees that were not to be found in bees from healthy colonies. 

 Microscopically, "no changes were discovered in the sahvary glands, brain, 

 fat-body, heart, tracheae, air-sacs, Malpighian bodies, or honey stomach." 

 Changes were found in the chyle stomach, however, and attention was con- 

 centrated on that organ. In film preparations made from small portions of the 

 chyle stomachs of diseased bees, teased out on glass shdes and stained with 

 methylene blue, a bacillus was found with darkly staining ends and a lightly 

 st&ining central band, resembhng Bacillus pestis in general appearance. This 

 was suggested as having a causal relationship to the disease and the name 

 Bacillus pestiformis apis was proposed. Cultures of this bacillus fed in sugar 

 to bees did not appear to have any harmful effect and the view that it is the 

 organism that caused the disease has been abandoned. 



B. Nosema apis. 

 In 1907 Dr Enoch Zander (1911) discovered a protozoon in bees which 

 was recognised as being closely related to Nosema bombycis, a parasite which 

 did enormous damage to the silkworm industry in France about the middle 



