12 BULLETIN 810, U. S. DEPARTMENT OF AGBICULTUEE. 



seems quite probable that the disease might in some cases be carried 

 over for months or even over winter through the medium of these 

 rubberlike scales. 



It is of interest to know that the amount of disease resulting imme- 

 diately from inoculations in which scale material is used is much less 

 than when larvae recently dead of the disease are used. This is true 

 also of dead larvffi stored in Petri dishes compared with smears allowed 

 to dry immediately from larvae recently dead of the disease. These 

 facts indicate a possible deleterious effect on Bacillus pluton of the sec- 

 ondary invaders multiplying in the decaying larvae. 



STREPTOCOCCUS APIS 



It is most probable that Streptococcus apis is the species that was 

 isolated from diseased brood by Burri (3) and referred to by him 



in 1906 as " guntheri-iorms." Maas- 

 sen described it in 1908 (8). The 

 organism grows well at incubator, 

 room, and refrigerator tempera- 

 tures in most of the media ordi- 

 narily used in the laboratory. 

 Its cultural characteristics suggest 

 the micrococci rather than the 

 streptococci. Confusion in some 

 of the earlier investigations was 

 due evidently to the resemblance 

 of Streptococcus apis and Bacillus 

 pluton morphologically. To this 

 FIG. z.-streptoooccu. avis. ^^ct is due the chicf interest in the 



species Streptococcus apis. Wlien 

 encountered in larvae dead of European f oulbrood it can be identified 

 readily by culturing. The generic position of this species should be 

 considered as being not altogether certain. 



Occurrence. — Streptococcus apis is occasionally encountered in larvse dead oC 

 European foulbrood and often is present in large numbers. 



Morphology. — It is more or less spherical (fig. 3 ; PI. VII, E), occurring singly 



and in pairs with occasionally a chain of 2 or more pairs when grown in liquid 



media. In larval remains not infrequently the ends may be somewhat pointed. 



Staining properties. — It colors uniformly and readily witli the common stains, 



and retains the stain after Gram's method. 



Glucose agar plate. — ^AYlthin a day growth is visible. Colonies never become 

 large. Surface colonies are usually less than 2 mm. They are circular with 

 uniform outline and a well-defined border, are grayish by reflected and bluish 

 by transmitted light, are smooth and convex, are moist and glistening in ap- 

 pearance, and are friable in consistency. When magnified the surface colonies 

 appear light brown in color, and granular in structure, the density decreasing 

 from the center to the periphery. Deep colonies appear dense, dark brown, and 

 coarsely granular. They are in general lenticular to oval but are sometimes 

 almost spherical in form. 



