MICROBIAL DISEASES OF INSECTS 931 



elongated bacillus forms, facing or more or less near this mass, of variable lengths 

 (cells 30 to 40/1 long have been observed); the round masses have also been ob- 

 served without the elongated bacillus forms. These giant forms, true forms of 

 growth, are only met with during the earlier period of infection; they disorganize 

 rapidly and give rise to many coccobacilli. At the beginning of their formation 

 the giant bacilli are slowly motile but as they continue to grow larger motility is 

 lost. The normal cells (coccobacilli), however, are very motile. The cultural 

 characteristics are as follows: in ordinary broth, abundant and rapid growth occurs 

 at 37, slight sediment after two days, no pellicle. Upon nutrient agar the colonies 

 are yellowish white, large, round, and somewhat raised. Saccate liquefaction. 

 Abundant growth on serum with rapid digestion from the second day. Milk is 

 coagulated the third day at 18-20, no digestion of casein. The following carbo- 

 hydrates are fermented, glucose, levulose, lactose, saccharose, mannit, maltose, 

 galactose, dulcit, and arabinose. Litmus carbohydrate media are more or less 

 decolorized with the exception of those containing glucose and saccharose. 



PATHOLOGY. The pathogenic action of B. lymantricola adiposa 

 manifests itself principally by the disorganization of adipose tissue. 

 About the fifth hour after inoculation the fat globules some of which 

 are yet contained in fat cells, begin to appear in the blood; the propor- 

 tion of these globules increases rapidly until the blood becomes milky. 

 This action upon adipose tissue is the first authentic example of this 

 type of specificity among microbial parasites of insects, yet this speci- 

 ficity is only very relative since this organism also multiplies abundantly 

 in the blood. 



PATHOGENICITY FOR OTHER INSECTS. The larvae of Vanessa 

 urticce, of the brown tail moth Euproctis chrysorrhea, and the silk 

 worm show the same symptoms upon inoculation as do the caterpillars 

 os Lymantria dispar. 



SAC BROOD, A DISEASE OF BEES 

 Filtrable virus White* 



HISTORY AND DISTRIBUTION. A disease which was similar to, but 

 was not foul brood was noted in 1881 by Doolittle in America, by 

 Jones of Canada in 1883, and by Simmins of England in 1887. The 

 larvae were found to die here and there throughout the brood comb; 

 the disease would disappear entirely or it would reappear the next 

 season; the bees would frequently remove the dead brood and no 

 further trouble would ensue. Simmins found no microscopic evidence 



* White. G. F. Sacbrood. Bull. 431, B. of Ent., U. S. Dept. Agr., 1917. 



