17 



Before going any further, I want to express my sincere thanks 

 to Dr R. Westling for aid in the determination of certain species 

 of moulds, and to Mr And. Norén in whose apiary most of the 

 feeding experiments were performed. 



1. Previous theories of the cause of bee-paralysis. 



In order to make clear the standpoint of Z änder (27, 28) with 

 regard to the nature and cause of bee-paralysis we have to consi- 

 der for a moment his investigalions of the so ealled dysentery in 

 bees (in Swedish : »Utsot»; German: »Ruhr»), a disease wellknown 

 to every bee-keeper in Europé as well as in America. He distin- 

 guishes between two kinds of dysentery, viz. the infectious or 

 Nosema disease (Nosema-Seuche»), and the noncontagious dysentery 

 (»Durchlauf», »nicht ansteckende Ruhr») that is, ordinary dysentery 

 or diarrhea. The latter kind is probably the most common in 

 Sweden, and is regarded by Zander to be merely a nervous reac- 

 tion in the bees brought on during the wintering of the bees by 

 annoying encroachment upon the colony, by queenlessness, or by 

 unsuitable winter food, e. g. food deficient of water. When mea- 

 sures of precaution are taken, particularly by supplying the bees 

 with sufficient quantities of water during the winter, this disease 

 can easily be prevented. The usual mark of dysentery, namely 

 the voiding of the excrements inside or outside the hive may, how- 

 ever, be a sign of the other kind of dysentery, viz. the contagious 

 Nosema disease caused by the tiny animal parasite Nosema apis 

 Zander, belonging to the Microsporidia and related to the organism 

 that gives rise to the Pebrine disease of the silkworm. In the fol- 

 lowing this disease will be called microsporidiosis, a name borrow- 

 ed from the English bee-literature and much to be preferred to 

 »Isle of Wight disease» which is its synonyme. 



The parasites live as amoebae in the wall of ventriculus during 

 the earlier stages of the disease. They pass låter on into a resting 

 stage and become enveloped in a thick and heavy spore wall. In 

 this form the »spores» are detached from the intestinal wall and 

 overflood ventriculus, which takes on a white and transparent color 

 from the masses of Nosema spores. In this stage they are easily 

 seen in the microscope as small, oval, strongly light reflecting 

 bodies. 



Svensk Botanisk 'Tidskrift 1917. 2 



