490 
Journal of Agricultural Research 
Vol.XXVI.No io 
Resistance and viability. —Bacillus noctuarum from a three-day bouillon culture 
is killed in a 2 per cent aqueous solution of carbolic acid in a few seconds; in a 1 per 
cent solution in two minutes; and in a 0.25 per cent solution growth takes place 
although retarded. The thermal death point in a similar culture is 54 0 C. exposed for 
10 minutes. The bacillus in a film produced by the evaporation to dryness of an 
aqueous suspension taken from agar is found to be dead very soon after becoming dry. 
The organisms from a similar suspension added to sand soon die if the sand is allowed 
to become dry, but if it is kept moist they remain alive for a long period. Old cultures 
on agar or in liquid media remain viable until the medium becomes dry. After 15 
months sealed agar cultures are alive and most likely will remain so very much longer 
if drying is prevented. 
FURTHER EXPERIMENTAL INOCULATIONS 
In seven experiments 20 cutworms of the genus Feltia were inoculated 
by puncture with material from worms sick or recently dead of cutworm 
septicemia. All of these died (pi. 2, A). Similarly 3 worms of the 
genus Agrotis and 2 of the genus Prodenia were inoculated and all of 
these also died. In the sick and dead worms Bacillus noctuarum was 
found in very large numbers in pure or nearly pure cultures. A pure 
culture was used in inoculating by puncture 8 cutworms in two experi¬ 
ments with the result that all of them died of septicemia. 
In four experiments 12 homworms were inoculated by puncture, using 
a pure culture of Bacillus noctuarum , and all of them died (pi. 2, M). 
Two of these worms kept at incubator temperature died within 20 hours. 
Likewise in seven experiments in which 20 silkworms were inoculated 
all of them died (pi. 2,1). A pine culture was used also in the inoculation 
of 8 catalpa moth larvae and all of these died within one day (pi. 2, J). 
Six cutworms were inoculated by the feeding method, using the tissues 
of worms sick or recently dead of the disease. None of them showed 
symptoms of infection or died of the disease. In two experiments 37 
silkworms in the fifth instar were fed leaves immersed in an aqueous 
suspension of a culture of Bacillus noctuarum , and of these 24 died, the 
maximum temperature at the time of the experiment being 34 0 C. In 
another experiment 24 silkworms in the second instar were similarly 
inoculated and none of them died, the maximum temperature during the 
latter experiment being 28° C. 
PATHOGENESIS 
Cutworms inoculated by puncture with pure cultures of Bacillus 
noctuarum become infected and show a mortality of practically 100 per 
cent. The period from inoculation to the death of the worm varies con¬ 
siderably, depending largely upon the temperature environment. At 
incubator temperature it may be less than a day, at room temperature it 
may be two or three days, while during cool weather this period may be 
even longer. In the few experiments performed with cutworms in which 
the feeding method of inoculation was used no deaths occurred. 
The susceptibility of the larvae of silkworms ( Bombyx mori L.) and of 
homworms ( Protoparce sexta Johan, and P . quinquemaculata Haw.) to 
experimental infection with Bacillus noctuarum is similar, the mortality 
being about 100 per cent where the puncture method is employed and 
much less when feeding inoculations are made. The larvae of the catalpa 
moth ( Ceratomia catalpae Bdv.) and grasshoppers (pi. 2, D) were also 
tested and found to be readily infected by puncture. No species tested 
was immune. 
