EXPERIMENT STATION BULLETINS. 295 



SYMPTOMS. 



Since the larvae affected with the disease usually die after the cells are 

 capped, American foul-brood is frequently well established in the apiary 

 before the beekeeper recognizes it. The first indication of a disorder in the 

 brood-nest is usually that of punctured and sunken cappings and a darkened 

 color of the diseased cells. In well advanced cases the "glue pot" odor is 

 frequently so pronounced that it can be easily recognized. Since the af- 

 fected larvae die at a time when they are beginning to transform into pupae 



Fig. 2. The ropiness of American foul-brood. From Farmers' Bulletin 442, U. S. Department of 

 Agr., Bureau of Entomology. 



they are found lying lengthwise on the floor of the cell with the back down. 

 Healthy larvae at this stage are white or slightly bluish in color, — appear to 

 glisten, and the skins are quite tough. Diseased larvae first change color 

 from the bluish-white of the healthy larvae to a light brown color. The 

 skin also becomes tender and is easily broken. As decay goes on, the color 

 changes to a more distinct brown, finally assuming a coffee color or chocolate- 

 brown shade. As the change in color of the larvae progresses the skin of 

 the larvae becomes more easily broken and the decaying material gradually 

 assumes a stickiness or ropiness which is one of the chief characteristics of 

 American foul-brood. The matter does not become distinctly ropy until 

 several weeks after the death of the larvae, but when decay has progressed 

 to the point where the remains commence to dry down into a thin "scale" 

 this ropiness is very characteristic. When a match or toothpick is applied 

 to the remains at this time it can be drawn out into threads from one to six 

 inches long. This cannot be done with the remains of larvae attacked by 

 European foul-brood, and is a distinguishing characteristic. As the decay 

 of the larvae progresses, another symptom to be noted is the presence of a 

 strong odor which has been frequently described as the odor of the glue-pot. 

 This is so pronounced that in advanced cases it can be detected when the 

 hive is first opened. Pupae dead of the disease, frequently have the tongue 

 sticking to the top of the cell. This is rarely if ever found in cases of Euro- 

 pean foul-brood. 



There are, then, three chief distinguishing features of larvae affected with 

 American foul-brood, namely, coffee color, ropiness, and the glue-pot odor 

 of the diseased material. 



After the decayed material has dried down on the bottom of the cell into 

 a thin layer loiown as the scale, it is not easily moved from the cell. How- 

 ever, there are occasional exceptions which may mislead the beekeeper. 

 One sample of foul-brood which microscopical diagnosis proved to be Amer- 

 ican contained scales which were so loose that they were shaken from the 

 comb. Another irregularity sometimes noted is that larvae are affected by 



