13^ 



to brood and to the queen. A hive population is continuously 

 undergoing renewal by loss of older bees and the production of 

 new bees. Recovery in a stock can be attained only by the failure 

 of the disease to spread amongst the young as the older die out. 

 The rate of spread varies in relation to factors at present unknown, 

 and, as far as appearances go, is further obscured by the rate 

 of production of new bees by the queen. When she is young and 

 prolific she may far outstrip the losses from disease, and the colony 

 may maintain itself so as to be profitable to the owner for a time. 

 When new bees cease to be produced the disease gains upon the 

 colony, and in this way the failure of stocks from the disease is 

 more common in autumn and in winter than at other times. 



The ordinary symptoms described above are not specific to the 

 conditions known as Isle of Wight disease, but appear to be usual 

 when adult bees are incapacitated from various causes. Hence 

 there are instances in which the bees of a stock may appear to be 

 suffering from Isle of Wight disease, and losses from crawling may 

 continue for several days or even a longer period. But in such 

 cases the non-infective nature of the trouble becomes apparent 

 when the later produced bees arc seen to be quite healthy. The 

 " disease " is then usually spoken of as having " passed off," and the 

 bees are said to have " recovered " from the disease. In Isle of Wight 

 disease in our experience there have been no recoveries of the sick 

 bees nor of affected stocks, although the rate of progress has been 

 very varied. The temporary sickness here referred to we have 

 observed on a number of occasions, sometimes widespread in a 

 district and affecting practically all the stocks. In such cases it 

 would appear to be due to some disturbing factor in the nectar or 

 pollen available at that time. We consider that May sickness, 

 which occurs in other months as well, is of the nature here described. 

 In other instances we have concluded that the failing of wintered 

 bees in spring has assumed the appearance of Isle of Wight disease. 

 Bees which have travelled long distances with ready facilities for 

 feeding sometimes show symptoms similar when eventually released. 

 Our later experiences have confirmed us in the view that Isle of 

 Wight disease is an infectious disease, but we have not found 

 Nosema apis to be causally related thereto. Experiments dealing 

 with this aspect of the problem are described in a succeeding 

 paper. 



