478 
Journal of Agricultural Research 
Vol.XXVI, No. ia 
In September, 1917, the writer began experimental studies on this 
disorder and these were continued with many interruptions until the 
present time (1922). The disease material used in the work was received 
from the laboratory at Clarksville. 
Homworm septicemia is of much interest, first, because it is a disease 
of two species of insects which are of great economic importance; and 
second, because it belongs to the large and important group of insect 
diseases of which the much discussed coccobacttlus infection in grass¬ 
hoppers is a member. Much is yet to be learned about this disorder, 
but the facts already obtained and given in the present paper will suffice 
to answer many questions likely to be asked concerning it. 
SYMPTOMS AND POST-MORTEM CHANGES 
The infected larvae lose their appetite. Their normal stool of berry¬ 
like pellets changes in the infected larvae to a semifluid one and then to a 
watery discharge. This dysenteric condition is one of the prominent 
signs of the disorder. Late in the course of the disease a thin “ vomitus ” 
oozes from the mouth. The pronounced turgidity seen in healthy worms 
becomes lost in the infected ones. 
A larva dead in the experimental cage following inoculation is usually 
found lying on its side occupying a slightly curved position. The remains 
of the larva that has died on the growing plant are found hanging usually 
head downward by means of the hooks of a proleg (PI. 1, A, B). The 
semifluid body content gravitates cephalad in this position. 
Soon after death the body of the worm becomes light brown, deepens 
rapidly to a dark shade, and finally turns almost black. The body wall 
at first resists puncture and tearing quite as much as during life, but 
later is more easily ruptured. The tissues within undergo a rapid change, 
becoming soon a brown semifluid mass in which silvery white portions 
of tracheae are seen. 
The body wall remains intact if the decaying larva is undisturbed. 
When drying takes place, the remains diminish in size but retain in 
general the larval form, becoming in a week or so, depending much on 
the climatic conditions, a dry, shriveled, friable, dark brown to black 
mass. 
EXCITING CAUSE OF THE DISEASE 
The media and methods commonly used in the laboratory are suffi¬ 
cient for the culture work. In the experimental inoculations the two 
methods not infrequently employed in insect studies have been followed. 
These may be designated as the puncture method and the feeding method. 
By the puncture method the body wall is pierced by a fine dissecting 
needle which is first sterilized by flaming and cooled, and the point of 
which is then contaminated by thrusting it into the tissues of the sick 
or recently dead larva or by dipping it into a culture, an agar one being 
most frequently used. Any convenient place on the body of the larva 
may be chosen for the puncture, the intersegmental spaces being as a 
rule the easiest to pierce. No attempt need be made to sterilize the 
area at the point of inoculation. The small amount of blood which the 
insect loses causes it no particular inconvenience. Control larvae punc¬ 
tured with a steille needle manifest no ill results from such a treatment. 
Likewise a larva punctured by a needle which has been dipped into the 
blood of another healthy larva or into unsterilized tap water suffers no 
