52 Annals Entomological Society of America [Vol. X, 



Apparently the activities of the insect and other animal 

 parasites of the diseased locusts were not affected. We were 

 able to rear several sarcophagid flies from diseased locusts and 

 a very large number of living Gordioidea emerged from the dis- 

 eased or dead insects. 



Other workers have tested the pathogenicity of Coccobac- 

 illus acridiorum for various other insects and have found that 

 not all insects are susceptible to the disease. 



D'Herelle found that chickens, guinea pigs and rabbits 

 were not susceptible and that man apparently suffered no ill 

 effects even when the cultures were carelessly handled. 



E. Experiments i?i the Laboratory. 



Experiments were performed in the laboratory in order that 

 we might become acquainted with the nature and action of the 

 disease before trying it out in the field. These experiments 

 were all carried out in breeding cages which were sterilized 

 before each experiment. 



The number of animal parasites, chiefly nematodes, and 

 Diptera, was exceedingly high, so it must be borne in mind that 

 several of the deaths recorded in these experiments may have 

 been due entirely to the parasite or to the fact that the resist- 

 ance of the locusts was lowered owing to the weakening action of 

 the animal parasites. 



Deaths which did not occur within a week to ten days were 

 considered doubtful because the percentage of deaths among 

 the checks confined for so long a time was fairly high. 



Experiment 1. Effect of Spraying the Insect with a Culture of 



Coccobacillus. 



Ten locusts were sprayed thoroughly. One died at the end 



of thirty hours, a second in two days, a third in three days, and 



at the end of eight days there were only five dead. The others 



remained alive for some time showing no symptoms of disease. 



Experiment 2. Effect of Contaminating the Soil. 



a. Twelve locusts were placed in a breeding cage containing 

 sand sprayed with a culture of C. acridiorum. One died at the 

 end of the first day. The others remained alive for several days 

 and showed no symptoms of disease. 



b. Several locusts were placed in an unsterilized cage from 

 which dead locusts had just been removed. No mortality was 

 produced. 



