30 BULLETIN 810, U. S. DEPARTMENT OF AGRICULTURE. 
By one or more of these colony symptoms manifested by larvee 
sick or only recently dead of the disease the experienced can diagnose 
European foulbrood definitely without a microscopic examination. 
The methods not only give definite results, but are also easy of 
application. They have been indispensable in much of the writer’s 
experimental work and it is believed that the beekeeper will find 
them to be valuable in practical apiculture where other gross meth- 
ods fail. 
BACTERIOLOGICAL EXAMINATION 
The findings from microscopic examinations and from cultures 
have been set forth in an earlier publication (10). These are always 
adequate for a definite diagnosis when a suitable sample is at hand. 
Bacillus alvei (p. 11) (fig. 2; Pl. VII, D, F) frequently overshadows 
all other species. In larve sick of the disease Bacillus pluton (PI. 
VII, A, B) overshadows all others. With experience one learns to 
recognize this species in stained preparations. The individuals are 
seen frequently in groups. They are more or less lancet shaped, and 
a variation, in size is often sufficient to be noticeable (fig. 1)... In 
larvee nearly dead and in those only recently dead Bactertwm eurydice 
(p. 18) (fig. 4; Pl. VII, C) is frequently encountered. Streptococ- 
cus apis (p. 12) (fig. 3; Pl. VII, E) occurs in a small number of 
cases. Bacillus orpheus (p. 14) (fig. 5; Pl. VII, H), B. vulgatus, 
and B. mesentericus are occasionally encountered. While B. pluton 
is present in all cases of European foulbrood, not infrequently in 
routine examinations it is so masked by the secondary invaders that 
the microscopic examination fails to reveal it. In many cases B. 
alvei and B. orpheus are recognized microscopically. Cultures are 
necessary for the differentiation of B. vulgatus and B. mesentericus. 
In many cases cultures are needed to differentiate Strep. apis and 
B. pluton. Strep. apis grows on the ordinary media, B. pluton 
does not. 
DIFFERENTIAL DIAGNOSIS 
AMERICAN FOULBROOD 
American foulbrood is recognized by the death of larve in capped 
cells and of pupe soon after transformation, the viscidity of the decay- 
ing remains of the brood, and, the “ foulbrood” odor which is fre- 
quently present. The presence of the spores of Bacillus carvae in 
large numbers and the absence of other species is conclusive proof 
of American foulbrood. 
1 Smears made from larve sick of European foulbrood and quite early in the course of 
the disease were selected in making a study of the morphology of B. pluton. These were 
stained with iron hematoxylin. In smears made from dead larve and stained with carbol 
fuchsin, as is usually done, the pointed ends and the more or less rod- -shaped forms are 
fess prominent than illustrated in figure 1, 
a "2 OT I 
