16 BULLETIN 204, U. S. DEPARTMENT OF AGRICULTURE. 
EXPERIMENTS IN DETERMINING THE INCREASE OF THE GIPSY MOTH IN THE FIELD. 
Iii view of the importance of parasites, disease, and unfavored 
food plants in reducing the increase of the gipsy moth, it seemed 
desirable to secure definite data on the normal increase of this insect 
in the field and the increase where these deterrent elements were 
present in varying degrees. The most feasible way to determine^the 
increase is to compare the number of egg clusters in a given locality 
from year to year. In order to do this arrangements were made in 
the fall of 1911 to study field conditions in a systematic manner. 
About 250 areas which have been designated as "observation points" 
were selected throughout the infested area. This gave an oppor- 
tunity for ascertaining the effect of latitude, seasonal variation, and 
altitude on the increase of the species. In selecting these points an 
attempt was made to secure as many pure stands of forest growth as 
possible; also, to obtain areas of mixed growth where the proportion 
of favored food plants varied. Areas were also secured where 
different species of parasites had been liberated and where the wilt 
disease had occurred abundantly or in a small amount during the 
previous year. The degree of infestation was also considered in 
making a selection and a number of points were obtained where the 
trees had previously been defoliated to check against some where no 
defoliation had resulted and the infestation was very light. After 
an area was selected a tree was marked for a center and a circle 100 
feet in diameter was laid out. Each tree within the circle was 
numbered consecutively and a note made of its species, size, and 
condition. In the fall, as soon as the foliage had dropped, a careful 
count was made of the egg clusters on each tree. These results have 
been secured and tabulated as well as exact information relative to 
the number of egg clusters found on the ground and undergrowth. 
Records have also been kept on the condition of the trees from year 
to year, and the number of trees which died in each area has been 
carefully noted. The condition of the territory surrounding these 
points, as regards infestation, has also been noted. This work has 
been supervised by Mr. C. W. Minott, but it has not been carried on 
for a sufficient number of years to give all the exact information 
desired. 
The following table gives the gross number of egg clusters. found in 
the points each year, and will be of interest as indicating in a general 
way the severity of the infestation from 1910 to 1914. 
It will be noted that 170 points are given in the table. The balance 
of the 250 which were originally selected have been discontinued, 
owing to destruction by fire, promiscuous cutting by the owners, or 
for other reasons. The area in the points aggregates 30.18 acres, 
and the surrounding territory which has been watched brings the 
total under observation un to 863.1 acres. For convenience, the 
