6 THE CAUSE OF EUKOPEAN FOUL. BROOD. 



sislike motion of their bodies is easily seen, but larvae of this same 

 age when sick frequently exhibit a marked ])eristalsislike motion of 

 their bodies which can be easil}^ seen with the unaided eve. Some- 



FiG. 5. — Sick larva which is more trans- 

 parent than a healthy larva of the 

 same age. (Original.) 



Fig. 6. — Healthy larva with dorsal wall 

 turned toward the observer showing 

 tlip narrow transparent area along the 

 median dorsal wall. (Original, i 



times the color of the larvic assi.sts in the selection of those that are 

 diseased. If, instead of the glistening white or bluish-white appear- 

 ance of healthy larva\ one ol).~erves some that are more transparent 



(fig. 5), or that possess a very 

 slight yellowish tint, frequently 

 such larva^ are diseased. In the 

 absence of the exaggerated peri- 

 stalsislike moveuient, however, 

 other tests should be applied, as 

 the color symptom is at times de- 

 ceptive. 



Figures 6 and 7 represent older 

 larva^ than the preceding. These 

 have turned themselves in the cell 

 so as to present a dorsal portion 

 to the observer. The narrow and 

 quite transparent area frequently 

 seen along the dorsal median line 

 of a larva serves often a useful 

 purpose in the diagnosis of Euro- 

 pean foul brood. In a healthy 

 larva (fig. 6) a i^oUen-colored intestinal mass is frequently plainly 

 visible through this transparent dorsal area. Microscopically this 

 mass is easily demonstrated to be largely pollen. If, however, upon 



Fig. 



-Sick larva of the age represented 

 in figure 6. (Original.) 



