1917] Studies on Coccobacillus Acridiorum D'Herelle 53 



Experiment 3. Effect of Contaminating the Food of 

 the Locusts. 



a. Seventeen nymphs were placed in a cage containing green 

 food sprayed with a culture of the organism. The food was 

 renewed daily and for several days it was sprayed either with a 

 pure culture of the coccobacillus or with a suspension of the 

 intestines of dead locusts. There were no deaths until the fifth 

 day, when one nymph died. After this there were a few deaths 

 at intervals. The experiment was discontinued at the end of 

 three weeks. The intestines of some of the living locusts were 

 then examined and C. acridiorum was found. 



b. Twenty locusts were fed with sweetened bran mash to 

 which a culture of the coccobacillus had been added. Two died 

 during the next day. By the seventh there were altogether 

 twelve dead and on the eleventh day lEifteen. The others sur- 

 vived for eight days after being removed to a clean cage. 



Experiment 4- Infection from Dead or Diseased Locusts. 



Experiments were tried to determine whether the disease 

 would spread readily from dead or diseased locusts to healthy 

 ones. To this end a number of healthy locusts were placed in a 

 cage with others that had just- died. The locusts used were 

 largely M. femur-rubrum with a few individuals of other species. 

 Nearly all the locusts failed to show symptoms of the disease. 



It was observed that occasionally a bivittatus would feed on 

 the dead insects. In order to determine the effect of this can- 

 nibalistic tendency on the spread of infection . we placed femur- 

 rubrum and bivittatus in equal numbers in a cage with dead 

 locusts. At the end of eight days 80% bivittatus were dead and 

 only 20% femur-rubrum. We have never in our experiments 

 observed any manifestation of cannibalism in any of the forms 

 of locusts and grasshoppers experimented on except M. bivittatus, 

 and in this case the tendency to prey on the feeble individuals is 

 not very marked. 



Experiment 5. Relative Resistance of Male and Female 



Locusts. 

 We were unable to observe any difference in the resistance 

 of male and female locusts. The following is an example which 

 shows how similar the two sexes are in the degree of 

 susceptibility : 



