10 CIRCULAR 3 9 2, U. S. DEPARTMENT OF AGRICULTURE 



part way up onto the bottom of the cells (fig. 5, G). There may be 

 a small raised swelling near the head end of the scale, but this rarely 

 is prominent. In advanced cases rows of cells contain dead larvae 

 uniformly in this position. 



When scales are numerous the disease can be diagnosed from their 

 appearance alone. Scales can be seen extended along the lower side 

 walls when the comb is held inclined so that a bright light falls on 

 the lower side walls and bottoms of the cells (fig. 1). Occasionally 

 cross markings which represent the segmentation of the larvae can 

 be seen on the scales. When completely dried the scales are brittle 

 and adhere so tightly to the cell walls that it is difficult to remove a 

 scale without breaking it. When death occurs after pupation has 

 started, the form of the pupa can be recognized in the scale (figs. 5, 

 H, and 6, F) . The mouth farts of the dead pupa may protrude from 

 the head of the scale and appear as a fine thread slanting slightly 

 backwards into the cell and at times adhering to the upper wall (fig. 

 5, F). The appearance of protruding or "stuck up" tongues is one 

 of the most dependable symptoms of American foulbrood. 



ODOE OF THE DEAD BEOOD 



In the first stages of decay, while the remains are still white, 

 practically no odor is detectable. When the remains begin to turn 

 brown and become ropy, however, an odor develops that is different 

 from the typical gluepot odor characteristic of the advanced stages 

 of this disease. In later stages, when the dead brood is brown and 

 decidedly ropy, the familiar gluepot odor is always present, but 

 it practically disappears when the scales are completely dry. In 

 advanced cases, when much decaying brood is present, the gluepot 

 odor can be detected even a foot or more from the combs. Since 

 the odor of American foulbrood is characteristic, the use of the odor 

 test is of considerable value in the diagnosis of doubtful cases. The 

 odor can best be judged by holding some of the decayed remains on 

 a toothpick at the entrance to the nostril and breathing deeply. 



EUROPEAN FOULBROOD 



CAUSE 



European foulbrood is an infectious bacterial disease of the brood 

 of honeybees. The bacteria grow within the stomach of infected 

 worker, queen, and drone larvae and cause their death, but pupae 

 are rarely attacked. Adult bees are not affected by this disease. 



The earliest studies on European foulbrood seemed to indicate 

 that it was caused by a rod-shaped bacterium, Bacillus alvei, which 

 is commonly found in decayed brood. Later it was observed that 

 lancet-shaped bacteria, different in shape and size from the rods and 

 spores of B. alvei found in decayed brood, are usually present in 

 large numbers in sick and recently dead larvae. This lancet-shaped 

 bacterium, which was given the name Bacillus pluton, is now com- 

 monly considered to be the cause of European foulbrood. It has 

 been found recently, however, that the rod-shaped B. alvei is capable 

 of changing its form to a lancet-shaped bacterium resembling B. 



