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17
Before going any further, I want to express my sincere thanks
to Dr R. Westuine for aid in the determination of certain species
of moulds, and to Mr Anp. Noren 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 ZANDER (27, 28) with
regard to the nature and cause of bee-paralysis we have to consi-
der for a moment his investigations of the so called dysentery in
bees (in Swedish: »Utsot»; German: »Ruhr»), a disease well known
lo every bee-keeper in Europe 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 liny 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 later 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
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