50 BULLETIN 780, U. S. DEPARTMENT OF AGRICULTURE. 
Very few objects are encountered in the microscopic examination 
of the stomachs that are likely to be mistaken for the spores of 
Nosema apis. Occasionally yeasts are encountered. They occur, 
however, in small numbers only, as a rule; a variation in size is 
usually to be observed; and if stained they take the stain readily 
and intensely. The writer occasionally has encountered small oval 
bodies resembling spores which escape from pollen grains. They are 
found in comparatively small numbers when encountered, however, 
and are smaller than Nosema spores. What these bodies are has 
not been determined. 
In examining bees that have been dead of Nosema-disease for some 
time a portion of the contents of the abdomen is suspended in water 
on a slide and examined microscopically. The highly refractive oval 
spores of the parasite will be found if the bee was Nosema infected 
at the time of its death. Younger stages of the parasite will not be 
encountered under these conditions. 
Stages of the parasite that precede that of the spores may be 
recognized at times from fresh preparations. Forms approaching 
spores in appearance, which have been referred to as young spores, 
together with growing or vegetative forms appearing frequently as 
though they were in pairs (PI. Ill, I), are seen occasionally. These 
younger forms are not likely to be recognized in preparations except 
in those made from bees recently killed and then only in small num- 
bers. They should not be depended upon in the making of the 
diagnosis. 
To determine very early stages of infection with Nosema apis the 
stomach of the suspected bee must be fixed, sectioned, and stained 
by laboratory methods. 1 The parasite is then found in the epithe- 
lial cells of the organ. 
Nosema-disease, like sacbrood, is quite prevalent among bees, and 
like sacbrood a small amount of infection may be present in a colony 
without producing any appreciable loss. When a diagnosis of the 
disease is being made in practical apiculture, therefore, considerable 
caution should be observed. A colony showing only a small per- 
centage of Nosema-infected bees and no other evidence of the disease 
is practically healthy. In reporting the presence of infection it 
would seem well to indicate in some way the amount of infection 
present. The percentage of infected bees among those examined 
might be given. 
l As a fixing fluid one containing a strong solution of mercuric chlorid can be recommended in studies 
on Nosema apis. Heidenhain' s iron hematoxylin is a very satisfactory stain for much of the vrork. Other 
fixers, especially those containing picric acid or formalin, have been used successfully. The sporesof 
Nosema apis are not readily stained hy all stains. Pyronin sometimes gives good results with methyl 
green as a counterstain. Alcoholic eosin applied for a considerable period, with methyl blue as a counter- 
stain, used on fixed smears made from fresh tissues, often results in desirable preparations. 
