22 Annals Entomological Society of America [Vol. XI, 



genus Schistocerca, whereas it may be impossible to establish an 

 epidemic in the field amongst members of certain other genera. 

 All of the workers reported that the bacteria they used were 

 pathogenic in their laboratory experiments. The field failures 

 may be due to differences between the habits of the members of 

 the genus Schistocerca and those of other genera. Differences 

 between the climates of the separate countries where Cocco- 

 bacillus acridiorum was used may also account for the varied 

 results. The natural immunity of different genera or species 

 is another factor worthy of consideration. Shall we therefore, 

 owing to several failures, condemn d'Herelle's method under 

 certain conditions? Obviously not. 



D'Herelle and other workers who used his organism and 

 methods successfully consider the following requirements the 

 most necessary to the rapid spread of the disease in the field. 



1 . Cannibalistic habits of the insects (as very frequently exhibited by 



the genus Schistocerca). 



2. Migratory habits (exhibited by the genus Schistocerca). 



3. Dense hopper infestation. 



4. Absence in hoppers of bacteria closely related to the Coccohacillus 



acridiorum. The presence of such organisms may have an 

 immunizing effect. 



5. Not an overabundance of normal food. When food becomes 



scarce due to the hopper infestation, the insects acquire can- 

 nibalistic habits which are favorable to the spread of the disease. 



6. High temperature. The disease spreads more rapidly at the 



optimum temperature. 



7. Absence of excessive rain. A heavy rain paralyzes the march of the 



epidemic. 

 All of the foregoing factors are undoubtedly highly important, but 

 the writer should like to add one more requirement absolutely 

 necessary for the study of this subject, namely: 



8. The use of the same organism by the different investigators. Care- 



fully controlled cultures should be distributed and used. The 

 ciiltural and especially the bio-chemical characters of Cocco- 

 hacillus acridiorum shovild be referred to constantly. Reference 

 to morphological characters solely, as has been done so often, is 

 worthless. 



During December, 1915, I received from Dr. L. O. Howard, 

 Chief of the U. S. Bureau of Entomology, two nutrient agar 

 tubes containing pure cultures of a bacterium. These cultures 

 were forwarded to Washington at the request of Dr. Howard 

 by Dr. Cicilio Lopez Ponce, representing the Secretary of the 

 Honduran Agricultural Commission of Tegucigalpa, Honduras. 



