x, B, 2 Barber and Jones: Coccobacillus acridiorum @Herelle 171 
Argentine—-the species of insects and the prevailing high 
temperature. 
Two species of locusts in mixed swarms were sprayed during 
these experiments; namely Gdaleus nigrofasciatus DeGeer, and 
Locusta migratoroides R. and F.2 The room temperature ranged 
from 28° to 32° C. or over during the time of these experiments, 
and the temperature in the fields exposed to the sun must have 
been much higher. Even during the short rainy period (the time 
when we attained a partial success) the temperature, though 
somewhat lower, remained relatively high. The author of the 
directions especially cautions against cultivating the organism at 
ordinary incubator temperature. If high temperature is an ob- 
stacle to attaining or maintaining an effective virulence of the 
bacterium, the method is much handicapped in the Philippines, 
where the insects often O28 through the nymph stage during 
the hot dry season. 
In order to determine whether or not our failure to obtain 
practical results with Coccobacillus acridiorum d’Herelle might 
have been due to some error in technique, the Bureau of Science 
sent to M. d’Herelle, at the Pasteur Institute, a detailed report of 
our 1913 experiments and their results. The following is an 
extract (translated from the French) of the reply kindly trans- 
mitted to the Bureau by M. d’Herelle and received November 
daa 9 13}: 
Your lack of success doubtless must be attributed to a lack of strength 
of the virulence. Dr. Sergent, director of the Pasteur Institute in Algiers, 
while working with Stawronoutus maroccanus, was obliged to obtain 56 
passages before obtaining a coccobacillus sufficiently strong to propagate 
the epizodtic in the field. As the locust in the Philippine Islands also 
belongs to a different genus from that of America, where the virus orig- 
inated, doubtless the passages must be multiplied in order to adapt the 
microbe (for use in the field). 
The directions accompanying the cultures stated that usually 
12 passages suffice to exalt the virulence to the necessary degree, 
but that the final test of virulence is that the coccobacillus be 
sufficiently virulent to kill the inoculated locusts within from eight 
to ten hours. We carried one of our series to the thirtieth 
passage, another to the fifteenth, and a third to twelfth. In 
a series conducted in May, 1914, in Mindoro by one of us 
a series was carried to the twenty-third passage. Judging 
by the time necessary for the bacterium to kill the inocu- 
lated insect, we had in all of the series a virus of fully sufficient 
exaltation. In reference to the experiments on the grasshopper 
* Identified by A. N. Condil, United States National Museum. 
