5i6 Journal of Agricultural Research voi.xni, no. io 



A microscopic study of smears from the dead animals readily precludes 

 the possibility of wilt. At times an animal will contract wilt as well as 

 the Japanese disease, but such cases are exceptional. Therefore, when 

 caterpillars which die from the new disease are examined, polyhedra are 

 not found, but large numbers of a streptococcus which the writer has 

 described under the name "Streptococcus disparts" are present. Sections 

 demonstrate that this bacterium, during the early stages of the disease, 

 is found throughout the alimentary tract. Later, and especially after 

 death, the intestinal epithelium disintegrates and ruptures, liberating 

 the organisms into the body cavity, where they invade practically all 

 the tissues. Naturally species of bacteria different from S. disparis are 

 also quite frequently found in the gut (intestinal flora), so that a pure 

 culture cannot be obtained by inoculating culture tubes with material 

 from the stomach or intestines. 



During the earlier stages of the disease, when the animals contract 

 diarrhea, the semiliquid feces everywhere soil the food plants. This fecal 

 matter is full of the microorganism in question, and is the principal cause 

 for the rapid spread of the infection. 



The writer has isolated 5. disparis many times from cases of the 

 Japanese disease and has never failed to reproduce the malady. The 

 organism was always again recovered by plating and other successful 

 infections performed with the pure culture. 



LABORATORY EXPERIMENTS 



Inoculation experiments were not thought necessary, for the reason 

 that the bacterium does not originally invade the blood of the insect. 

 5. disparis invades the alimentary tract with the ingested food, and 

 therefore food-infection experiments were considered more instructive. 



Tables I to III are self-explanatory. The animals used in the experi- 

 ments came from a selected stock of American caterpillars from which the 

 wilt disease had been nearly eliminated. Gipsy-moth caterpillars taken 

 directly from the field can not be used for experimentation, for large 

 numbers are invariably infected with wilt. A stock of caterpillars 

 comparatively free from this disease must first be produced by selection 

 and this, as the writer has shown in a previous publication, takes at least 

 three years. Each animal used in the streptococcus experiments was 

 isolated in a separate sterile glass fruit jar and the food foliage was shipped 

 daily from a region where the gipsy moth does not occur. This latter 

 precaution was taken in order to preclude the introduction of wilt. The 

 nutrient bouillon cultures were diluted one-half with sterile water and 

 sprayed on the foliage by means of a fine atomizer until the leaves were 

 visibly wet. Controls accompanied all of the experiments and are 

 absolutely necessary to the proper interpretation of all disease experi- 

 ments with insects. 



