Dec. 8,1923 
Cutworm Septicemia 
491 
Hornworms inoculated in 1921 with a culture 0 of Bacillus noctuarum 
that was isolated in 1917 died in practically the same period as did the 
worms inoculated with the same culture in 1917. With this culture 
silkworms were inoculated each year from 1918 to 1921 and all of them 
died, the period from the inoculation to the death of the worms being 
about equal in all instances. No important change in virulence, there¬ 
fore, has yet been observed in B. noctuarum kept on artificial media for 
four years. 
Once Bacillus noctuarum gains entrance to the blood of the larva it is 
seen that a fatal outcome under the usual environmental conditions is 
almost inevitable. That the tissues possess some protective agencies, * * 7 
however, seems probable from observations already made. In microtome 
sections evidence is gained that in the infected larva a phagocytosis occurs 
which tends to give some protection to the host. This phenomenon is 
suggested by the presence of cell groups (PI. 1, G) in the blood spaces of 
the sick worms. Some small groups are found in cutworins within one day 
following a puncture inoculation and after two days the number and size 
of the groups have increased. The number of groups in a section is never 
large, only two or three and sometimes none at all being present. Their 
size varies from 40 to 150 microns in diameter or even more. The smal¬ 
ler groups consist of cells arranged about a single center, while the larger 
ones may have a conglomerate structure, two or three centers being seen 
in one section of the group. The cells making up the centers are more or 
less spherical while the others are somewhat spindle-shaped and arranged 
in a concentric fashion about a center or group of centers. The same 
phenomenon is observed in cutworms (PI. 1, H) and in hornworms 
(PI. 1,1) inoculated with B. sphingidis. As might be expected in insects 
as different as are cutworms and hornworms, some differences in the 
details of the phenomenon are to be found in the two species of worms. 
While satisfactory direct ocular proof demonstrating that these cell 
groups are performing the function of phagocytes is yet wanting, there 
are certain facts at hand which tend to indicate strongly that they are 
doing so. These are as follows: (a) Cells with phagocytic power are 
generally recognized as being present in insects; (b) the cell groups are 
found in inoculated larvae and not in uninoculated ones; (c) different 
investigators have recorded observations to the effect that phagocytosis 
occurs in bacterial infections; and (d) Speare 8 has shown in fungous 
infections of cutworms the presence of cell groups which are very similar 
in structure to those seen in these bacterial infections of this worm, the 
fungi being easily recognized within the cytoplasm of many of the cells. 
A rabbit inoculated intravenously with 1 cubic centimeter of a 
normal salt suspension from a 24-hour agar culture, containing about 
100 million organisms, showed an impaired appetite on the following 
day, from which it readily recovered. An autopsy on the etherized 
animal, performed more than a month after inoculation, revealed only a 
few unimportant lesions. 
• The culture was on agar kept at room temperature and shielded from the light, transfers being made 
two or three times a year. 
7 Much indeed is yet to be done on immunity in insects. The problem is recei ving some attention at 
present by different investigators, prominent among whom are Paillot and Metalnikow in France. 
•Speare, A. T. further studies of sorosporeixa uveiaa, a fungous parasite of NOCTUID 
dtARVAj. In Jour. Agr. Research, v. 18, p. 417-422. 1920. 
71687—24 - i 
