179 



occurred so extensively that "by 1912 it had reduced the 

 number of locusts to such an extent that no invasion into 

 Mexico occurred. D'Herelle succeeded in isolating the 

 "bacterium responsible for the epizootic from the intestinal 

 contents of dead locusts, the same organism not occurring 

 in healthy specimens. D'Herelle found further that locusts 

 artificially inoculated with this organism died with the 

 characteristic symptoms. However, Mereshkovsky (1925), 

 Pospolov (I926) and others have expressed the "belief that 

 Coccobacillus acridiorum is a normal "symbiont" of the 

 "blood of locusts, which can, under certain conditions of 

 temperature and humidity, "become a dangerous parasite. 



Coccobacillus acridiorum is a pleomorphic "bacillus with 

 coccoid forms (0.^ to 0.6 microns) and "bacillary forms 

 (0.9 to 1.5 microns) appearing in the same culture. In 

 young cultures and in the intestinal contents of the locust 

 the coccoid forms are the most abundant. Many cultures 

 have "been considered to "be Coccobacillus acridiorum when 

 in reality they were^ not. This has "been "brought out "by 

 Glaser (1918) in a systematic study of the organisms 

 placed under the name of Coccobacillus acridiorum d'Herelle. 



Since d'Herelle' s early successes some investigators 

 have "been able to confirm his results while others have 

 not. For one thing, there seems to be a difference in - 

 susceptibility of different locusts to the disease. The 

 bacteria appear to be more effective against locusts 

 belonging to the genus Schistocerca than against other 

 genera of the Locustidae. Species of the genus Caloptenus 

 in Argentina and Stauronotus maroccanus in Algeria have 

 been found to be experimentally susceptible. D'Herelle 

 apparently was successful in combating plagues of Schisto - 

 cerca paranensis in Argentina. In 1915 d'Herelle controlled 

 an outbreak of Schistocerca peregrina in Tunisia by a com- 

 bination of mechanical methods and the use of his organism. 

 Experimentally the organism was found to be pathogenic for 

 Schistocerca paranensis and Tropidacris dux in Trinidad 

 (Rorer, 1915) • Glaser (1918) found that a certain strain 

 of Coccobacillus acridiorum ( "Souche cham*) was pathogenic 

 to Melanoplus atlantis , and to Melanoplus bivittatus and 

 Melanoplus femurrubrum to a lesser degree. Another strain 

 ( "Souche Sidi" ) was less pathogenic to Melanoplus atlantis 

 and Melanoplus bivittatus than the "Souche Cham" strain. 



Among the insects which were slightly or not at all 

 susceptible to wholesale destruction by Coccobacillus 

 acridiorum are: Pachytylus ( Locus ta ) migratoroides ( Mackie , 

 1913)7 Zonocerus elegans (Lounsbury, 1913)> and Oedalens 

 nigrofasciatus (Barber and Jones, 1913)* 



