32 
2. 
10. 
Ge 
12. 
13. 
14. 
15. 
BULLETIN 810, U. S. DEPARTMENT OF AGRICULTURE. 
All larvee-——worker, drone, and’ queen—are susceptible to the dis- 
ease; adult bees are not. 
. Man evidently is not susceptible to infection with Bacillus pluton 
nor are the experimental animals. 
. As far as is known insects other than bees are not susceptible. 
. Brood can be infected by feeding the colony a suspension of 
crushed larve sick or dead of the disease. This is described in 
the present paper as the indirect method. 
. The virus contained in a single larva recently dead of European 
foulbrood will produce a considerable amount of disease when 
fed to a colony. 
. The larve can be infected also by a more direct method. A 
fraction of a drop of a suspension of the stomach contents of 
a larva sick of the disease added with a capillary pipette 
directly to the food surrounding the larva to be inoculated 
will result in infection. 
. Bacillus pluton gains entrance to the larva by way of the mouth. 
The growth and multiplication of the parasite take place 
within the stomach (mid-intestine) of the larva and do not, 
during the life of the larva, get beyond the peritrophic mem- 
brane. The tissues, therefore, are not invaded by it. 
. The secondary invaders in European foulbrood, Bacillus alvei, 
Streptococcus apis, Bacterium eurydice, and. Bacillus orpheus, 
rarely, if ever, invade the tissues until the larva is dead or 
nearly so. In a few instances in microtome sections rod forms 
have been encountered in the act of invading the tissues of 
living larve. The species, however, was not determined defi- 
nitely. 
The period of incubation is slightly less than 3 days. 
Brood is susceptible to infection at all seasons of the year. 
More brood die of the disease during the first half of the brood- 
rearing season than during the second half. 
The writer has examined samples of the disease from Canada 
and the United States. From written reports it seems quite 
certain that it occurs also at least in Denmark, England, Ger- 
many, France, and Switzerland. 
Occurring as it does in this somewhat wide range of climatic 
conditions, the presence of the disease in any particular locality 
can not be attributed entirely to the prevailing climatic con- 
ditions. 
The quality of food obtained by the bees does not affect greatly, 
if at all, the course of the disease in the colony, although the 
quantity may affect it to a variable extent. 
— 
ee 
