MICROBIAL DISEASES OF INSECTS 911 



not affected. This organism is distinct culturally and biochemically from the 

 organism, Diplococcus lymantrioe recently described by Paillot which is also parasitic 

 in the gipsy moth caterpillar, and moreover is highly pathogenic to the caterpillars 

 while D. lymantrice is not very pathogenic. 



METHODS OF INFECTION. During the earlier stages of the disease 

 when the caterpillars contract diarrhoea, the semiliquid faeces every- 

 where soil the food plants. This fecal matter is grossly contaminated 

 with the streptococcus, and is the principal cause for the rapid spread 

 of the infection. 



PATHOLOGY. 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 disinte- 

 grates and ruptures, liberating the organisms into the body cavity 

 where they invade practically all the tissues. 



Microscopically striking changes can be noted in the muscle tissues 

 even in the early stages of the disease. Normal muscle tissue shows 

 clearly the striae but in the early stages of the disease these show less 

 clearly and the individual fibrillae seem to be loosely arranged. Later 

 stages of the disease show first an absence of the typical striated ap- 

 pearance due to the fact that the fibrillae have lost their compactness 

 and have separated from one another like threads of cotton; the arco- 

 lemma disintegrates gradually with the rest, and the nuclei of the cells 

 lose their normal positions and become scattered. Up to this time it 

 can be safely predicted that Strept. disparis will be found in the ali- 

 mentary tract. Then finally, the muscle tissue disintegrates com- 

 pletely, the fibrillae, etc., are no longer visible, and the whole simulates 

 coagulated protein material with minute granules scattered throughout. 

 When this stage in muscular disintegration has arrived, nearly all of 

 the other tissues have likewise disintegrated more or less, and Strept. 

 disparis may now be seen scattered everywhere. 



Field experiments were conducted with Strept. disparis in sections 

 of the gipsy-moth infested territory many times with success. In two 

 places quite a severe epidemic was created. A large amount of work 

 still is needed, however, to determine the relative importance of this 

 method of combating the gipsy-moth. 



