Ql8 MICROBIAL DISEASES OF INSECTS 



Selenopsis gemminata, near Buenos Aires was annihilated in 1912. 

 Several drops of the culture were placed in each ant hill. 



A tta sexdens, a veritable plague in the tropical and sub-tropical 

 countries was annihilated at Chaco and Tucuman after the virulence 

 had been increased for this species of ant by many passages. 



III. CATERPILLARS. A field of cotton which was being ravaged by 

 caterpillars was treated with B. acridiorum. Four days afterward all 

 the caterpillars were dead while a neighboring field, treated simul- 

 taneously with Paris green, still contained many living caterpillars. 



The yellow bear caterpillar (Spilosoma) Diacrisia mrginica) has 

 been found to be susceptible. (DuPorte and Vanderleck). 



B. acridiorum does not attack the silk- worm, Bombyx mori; it kills 

 the cockchafer, Melolontha vulgaris, by injection but not by ingestion. 



Birds and mammals in general are immune to this bacillus. 

 One notable exception is the sewer rat which dies from generalized 

 septicemia a few hours after injection. The rat was immune to cul- 

 tures ingested. 



IV. BEETLES. The Colorado potato beetle, both larvae and adults, 

 is not susceptible. (DuPorte and Vanderleck). 



BACILLARY SEPTICEMIA OF THE CATERPILLARS OF Arctia caja L. 

 Bacillus cajce Picard and Blanc* 



HISTORY AND DISTRIBUTION. In 1913 the vineyards of central 

 France were almost completely destroyed by two diseases; one of these 

 was a fungus disease caused by Empusa aulica, the other was a septi- 

 cemia of bacillary origin. 



SYMPTOMS. The caterpillars become flaccid and emit a nauseating 

 odor; their digestive tube contains only a clear liquid free from all 

 organisms. The blood contains a pure culture of a bacillus with which 

 the disease has been produced artificially. 



CAUSAL ORGANISM. B. caja is a slightly oval bacillus, about 1.5/1 in length; 

 motile; Gram negative; stains deeply with crystal violet; treated by Pappenheim's 

 method it shows a characteristic bi-polar stain. 



* Picard, F. and Blanc, G. R. On a bacillary septicemia of caterpillars of Arctia caja L. 

 Compt. rend. acad. sci. 156, 1913, pp. 1334-1336. 



