100 PSYCHE [October 
Bearing in mind the close relationship existing between this pest and the Gypsy 
Moth, and realizing that, in the entire animal world, one of the greatest checks to over- 
production is the appearance of epidemic diseases, I attempted to put Fischer’s con- 
clusions regarding the artificial production of flacherie, to a practical test. This was 
done by the following series of experiments on the Gypsy Moth. Several thousand 
caterpillars from normal overwintered eggs were reared, from the time of hatching, 
under the best possible conditions, each egg-mass being kept separate. Immediately 
after the second molt, the larvae were removed, with the exception of small control 
series, and those from each egg-mass divided among isolated trees, in such a manner 
that each tree received caterpillars from only a single egg-mass. The isolation of the 
individual trees was accomplished by means of a board ring about ten centimeters 
high, smeared with tanglefoot to prevent the caterpillars from crawling over, and 
large enough to include all perpendicular lines dropped from the tips of the outer- 
most branches. Previously, of course, each tree had been carefully cleared of any 
foreign caterpillars, and care was taken to utilize only such trees as had been only 
slightly or not at all damaged by caterpillars the previous year. Oaks, birches and 
apple trees were used. About four days after the second molt fifty caterpillars 
altogether were removed from these various trees and placed in a small breeding cage. 
There they were fed on their normal food plant, oak, but upon leaves which had 
been previously soaked with the attached small twigs in water for four days. After 
six days of such feeding, I recognized the sweet odor which is the early symptom of 
flacherie, and two days later the first dead caterpillars were to be seen. ‘Two days 
later still, I counted twenty dead specimens, which I distributed, together with those 
still living, upon three isolated trees (oak, apple and birch). On the next day the 
first death on these trees occurred, and in this experiment by the time of pupation, 
_ the mortality had reached fifty-five to sixty percent. 
In a similar way a second experiment was made, but with caterpillars which 
had not yet passed the fourth molt. Among these, the early symptoms of the disease 
were noticeable as early as the second day, and the first dead specimens were to be 
found two days later. With the dead and diseased larvee of this series, the cater- 
pillars of the same age on three trees (oak, apple and birch) were infected. In this 
case the disease made more rapid headway, but the proportion of dead specimens 
at the time of pupation exceeded that of the first experiment by only five percent, 
that is to say, it amounted to sixty-five percent. 
A third experiment was then undertaken in the following way: to twenty-five 
caterpillars, taken just after death at which time they turn into a thin semi-liquid or 
jelly-like mass, two liters of water containing a small quantity of glue were added. 
