FUNGOUS DISEASES OF THE HONEYBEE 33 



Other yeasts isolated from bees, including S. elUpsoideus, S. 

 cerevisiae, Mycoderma cerevisiae I, and M. cerevisiae II, three un- 

 identified yeasts, as well as brewer's yeast, gave results similar to 

 those with S. apiculatus. 



The highest death rate was obtained with S. elUpsoideus and 8. 

 cerevisiae. With both of these organisms the first symptoms of 

 disease appeared in from 24 to 36 hours at normal room temperature, 

 although at 30° C. this time was shortened. The highest death rate 

 occurred during the second to fourth day after inoculation, and a 

 few bees died between the fifth and sixth days. With these two 

 organisms from T5 to 100 per^ cent of the bees inoculated usually 

 died from infection. 



With MycodervtM cerevisiae I, M. cerevisiae II, and the three un- 

 identified yeasts from bees, the death rate from infection was slightly 

 higher than with Saccharomyoes cupiculatvis. Infected bees rarely 

 lived longer than seven days after the inoculations were made. From 

 50 to 70 per cent of the inoculated bees died as a result of infection. 



Microscopical examinations wert made of the thoracic muscles and 

 blood of inoculated bees at intervals after inoculation. Yeast cells 

 multiplied rapidly within the blood and at the time of death were 

 present in such large numbers that the blood appeared millcy. 

 Although the organism was ultimately carried to all of the body 

 divisions by the blood, the most abundant development seemed to 

 occur on the muscle fibers of the thorax. Yeast cells seemed to 

 multiply there while the blood flowed over them without altering 

 their position. 



In a few cases the infection appeared more or less localized in the 

 region surrounding the point of inoculation. With S. apiculatus, 

 small spindle-shaped to linear pockets filled with yeast cells were 

 observed in considerable numbers between the fibers of the wing 

 muscles and apparently between the sarcostyles near the surface of 

 the muscle fibers. There were usually from 5 to 20 yeast cells in 

 each of these pockets at the time death occurred. 



Symptoms were readily discernible upon dissection of the bees 

 after death. The blood was found to have lost its pale-brownish 

 color and had become milky. At the time of death, the wing muscles 

 were slightly less rigid than in normal bees. Later they became 

 mummified and brittle. The drying wing muscles shrink away from 

 the exoskeleton except where they are attached. One of the most 

 distinctive symptoms of yeast infection determinable without the 

 aid of a microscope is the presence of a chalk- white coating on the 

 surface of the muscles after they have dried. The presence of nu- 

 merous yeast cells within the blood and on the muscle fibers is readily 

 established with the aid of a microscope. No external changes were 

 observed by which bees dead of infection with yeasts could be distin- 

 guished. 



DISCUSSION 



These investigations have dealt with the fungi for which patho- 

 genicity has been established and those that are closely associated 

 with bees but usually do not parasitize them. All of these ordinarily 

 reach their typical development as saprophytes under a wide variety 



