HORNWORM SEPTICEMIA 1 
By G. F. White 
Specialist in Insect Diseases, Bureau of Entomology, United States Department of 
Agriculture 
INTRODUCTION 
The larvae of two species of insects, Protoparce sexto Johan, and Proto- 
pence quinqmmaculaia Haw., of the family Sphingidae, are frequently 
called homworms, a name suggested by a large, curved, hornlike spine 
on the dorsal and posterior portion of the body. They are the large, 
naked, green “worms” 3 which feed so greedily on the leaves of growing 
tobacco and are then commonly called tobacco worms/ When they 
feed on the tomato plant they are often referred to as tomato worms. 
The potato and eggplant also furnish food for them. 
A disease sometimes occurs among homworms. The remains of the 
larvae that die of the disorder darken soon after death and as a result 
of drying become a black, mummified, shriveled mass. During the course 
of the disease ip these larvae a bacterium may enter the blood stream and 
multiply rapidly therein to a marked degree. This septicemia is one 
of the most pronounced characters of the disorder and suggested the 
name “homworm septicemia” which is here given to the disease. 
Very little literature is found regarding the diseases of homworiUS, and 
at the present time it is not possible to know definitely whethet the 
existence of the disorder described in this paper has heretofore been 
recorded. Garman (j, p. 30 ) 3 in 1897 states that he has: 
Sometimes observed dead and blackened worms clinging to the plants, head down, 
by means of the hooks on their fleshy legs, * * *. 
The presumption indicated by him, however, is that they had died 
of a fungous infection, and he cites observations made by Thaxter 
(6, p, 96) in 1890. Lovett (4, />. 171) states that: 
A bacterial disease sometimes attacks these worms, causing them to shrivel up, 
turn black, and die. 
A similar statement is made by Reed (5, />. 26). 
A. C. Morgan and his coworkers at the tobacco insect laboratory of 
Southern Field Crop Insect Investigations, Bureau of Entomology, at 
Clarksville, Tenn., encountered this disease and observed that it could 
be transmitted to healthy larvae by the puncture method of inoculation. 
In a letter Mr. Morgan writes: 
In 1917 some special experiments with nearly mature homworm larvae were ruined 
because of the rapid spread of homworm septicemia in the experimental cages. Since 
that year no great numbers of larvae have been under observation at any one time 
except in hibernation cages. Although the disease has always been in evidence 
in the hibernation cages, yet it has never been sufficiently severe seriously to affect 
the experiments. I do not believe that this disease is of much economic importance 
in this region, for diseased larvae are rare under natural conditions. 
1 Accepted for publication October a, 1923. 
1 For convenience the term “vronns” is used frequently in this paper as an abbreviation of “hornwonns.” 
•Reference is made by number (italic) to “ Literature cited," p. 486. 
Journal of Agricultural Research, 
Washington, D. C. 
ahz 
71687—24—3 
Vol. XXVI, No. xo 
Dec. 8,1923 
Key No. K-zx8 
(477) 
