60 BULLETIN 780, U. S. DEPAKTMENT OF AGRICULTUKE. 



Very few objects are encountered in the microscopic examination 

 of the stomachs that are Hkely 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 readUy 

 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 encoiuitered, 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. Yoimger 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 yoimg 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.^ 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-inf ected 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. 



'Asa fixing fluid one containing a strong solution of mercuric chlorid can be recommended in studios 

 on Nosema apis. Heidenhain's iron hematoxylin is a very satisfactory stain for much of the work. Other 

 fixers, especially those containing picric acid or formalin, have been used successfully. The sporesof 

 Nosema apis are not readily stained by all stains. Pyronin sometimes gives good results withmethyl 

 green as a counterstatn. Alcoholic eosin applied for a considerable period, ■u-ith methyl blue as acounter- 

 stain, used on fixed smears made from fresh tissues, often results in desirable preparations. 



