492 
Journal of Agricultural Research 
Vd. XXVI, No.io 
COMPARISON OF BACILLUS NOCTUARUM, B. SPHINGIDIS, AND B. 
ACRIDIORUM 
The morphology of Bacillus noctuarum (pi. i, A, B), B. sphingidis 
(pi. i, C, D), and B. acridiorum (pi. i, E, F) is very similar. Their 
cultural characteristics, while slightly different (Table I), show that 
they are closely related species. Cutworms (pi. 2, A, B), grasshoppers 
(pi. 2, C, D), silkworms (pi. 2, G, I), catalpa moth larvae (pL 2, H, J), 
and hornworms (pi. 2, K, L, M, N) inoculated by puncture with 
pure cultures of B. noctuarum and B. sphingidis , respectively, died in 
each instance from septicemia. Similarly grasshoppers (pi. 2, E, F) 
and hornworms (pi. 2, O, P) inoculated with B. acridiorum died from 
infection with this species. The virulence of B. noctuarum and B. 
sphingidis were almost equal, while that of B. acridiorum , at the 
time of the experiments at least, was less. 
, The serum of a rabbit immunized with Bacillus noctuarum and showing 
an agglutinin titer of 1:3,200 for the culture used did not agglutinate 
B. sphingidis at any dilution, and the serum of a rabbit immunized with 
B. sphingidis and showing a titer of 1:4,000 for the culture used did not 
agglutinate B. noctuarum at any dilution. Neither of the immune sera 
would agglutinate the “souche sidi” or “souche cham” strain of B. 
acridiorum . 
From the foregoing observations it will be noted that the morphology, 
cultural characteristics, and pathogenesis of Bacillus noctuarum , B. 
sphingidis , 9 and B. acridiorum are quite similar, being sufficiently alike 
to place them in the same group of organisms, an important one consist¬ 
ing of species associated with septicemias encountered among many 
insects. Serologically, however, the three species are quite different. 
It is not unlikely that when further studies have been made on cut¬ 
worm septicemia other strains of Bacillus noctuarum will be encountered 
which differ from the one described here. 
PREDISPOSING CAUSES 
The results obtained from the study of the exciting cause of cutworm 
septicemia recorded above and the knowledge at hand concerning other 
insect diseases belonging to the same group of disorders lead one to be¬ 
lieve that in the causation of the disease the exciting cause receives much 
aid from predisposing factors. That these contributing causes are im¬ 
portant is evident, the problem being one of the interesting ones yet to 
be solved. 
It seems probable that the incidence of the disease in nature varies 
somewhat with the seasons. High temperature is probably also a con¬ 
tributing agent. Data are yet wanting to show definitely the value of 
the different instars as predisposing factors. The facts at hand indicate 
that larvae in the last stage are more susceptible than they are in any of 
the other instars. Differences that exist in the susceptibility of the 
different species and genera of cutworms to infections are likewise not 
yet established. 
• In giving two names to two cultures so similar as are B. noctuarum and B. sphingidis the writer has 
followed the example of other workers who have encountered and studied different members of the inter* 
esting group of bacilli to which these belong. When this group is more completely worked there may de¬ 
velop good reasons for changing the specific classification that is being made. 
