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of the case permitted. Great results had been anticipated by some 
from an introduction of the disease of the Cabbage Worm (Pieris rcvpce) 
as a remedy for destroying the Cotton Catterpillars (Aletia xylina) or 
the Boll Worm. Upon investigation it was found that this disease 
had already been introduced with its host through the natural dissemi 
nation of the disease from the locality of its first appearance. The 
third complication arose when it was observed that about 80 per cent 
of the larvse of Plusia brassicce, a very common cabbage insect in the 
South, were dying of disease. The importance and relation of these 
three conditions to each other will be better appreciated by bacteriol- 
ogists when it is explained that the system of small negro tenantry, 
which is customary in the greater portion of the cotton district, results 
in numerous small garden patches along the edges of, and often within, 
the centers of the fields. The one vegetable which can safely be pre- 
dicted to be present in nearly all of them is cabbage. These plants 
were always infested with either Pieris rapcv or Plusia brassicce, or 
both, and concerning both it was known that disease made its appear- 
ance. The Boll Worm and Cotton Catterpillar were therefore con- 
stantly exposed to the danger of infection. As a consequence, in the 
studies for the artificial infection of the Boll Worm, the following 
sources of error required elimination: First, infection through its own 
peculiar germ ; second, through that of Pieris rapce, and, third, through 
that of Plusia brassiew. This could be best guarded against by deter- 
mining, as much as possible, the relation of the three germs to the three 
insects involved. Before these points are discussed, it is advisable to 
dwell upon some other conditions of environment which will contribute 
to a better interpretation later. 
It is asked, why does not the disease of the Boll Worm itself spread 
more freely? The diseased Boll Worms, with few exceptions, were 
found in ears of coin. Here, as has been stated in the first part of this 
report, a struggle for food, due to crowded conditions, may and often 
does occur. This compels more or less traveling in search of suitable 
quarters. This in turn increases exposure to all sorts of unfavorable 
conditions, including the attack by parasites and natural enemies, as 
well as disease. Further, having probably fought for its freedom, the 
larva is forced to change at a time when it is weak and least fit to resist 
such conditions. It is under these conditions that the Boll Worm some- 
times falls a victim to disease, usually, however, getting under the 
cover of another ear before dying, thereby lessening the chances for its 
infecting others of its own species. In view of these facts, the trap-corn 
method recommended in another portion of this report becomes an im- 
portant factor, in that for this species it furnishes those conditions 
which are iavorable for the greatest propagation of disease. 
When the Boll Worm infests cotton, the chances for infection are even 
more diminished, in that each individual becomes a hermit in addition 
to feeding on the inside of the cotton boll. Upon cotton they seldom 
