April, ’24] hartzell: interpretation of codling moth data 183 
Method of Collection of Data on Damage 
The same trees on which records were kept in the observation points 
were under observation during the years mentioned in order to determine 
the damage that was resulting from defoliation. Nearly all the species 
of forest and shade trees common to New England were included in 
these areas. Each tree was rated at the beginning of the experiment as 
either good, fair, poor or dead, based on the condition of foliage and 
apparent vitality of the subject. Annual records were made in July 
of the percent, of defoliation of each tree and later in the season its 
condition was rated. 
Three men were ordinarily used on this work. The man in charge of 
the party kept the notes while the other two made the ratings. Each 
tree was rated separately by each man and the tally was averaged. 
Ratings on the percentage of defoliation or condition of the trees are 
difficult to secure accurately. By averaging the ratings of two or more 
men data that was more dependable was obtained. 
During the ten years that this experiment has been under way many 
of the trees have been defoliated and have died. In some cases the 
owners have desired to salvage the areas in which the observation points 
were located and this has resulted in clean cutting operations. 
About one-half of the points have now been cut or it has been neces¬ 
sary to abandon them because practically all of the trees have died. 
Damage by the Gipsy Moth is not confined to the actual killing of 
trees. There are many cases where trees are partly defoliated and suffer 
retardation of growth from this cause. 
Increment borings of typical trees have been secured and the speci¬ 
mens studied to determine the loss in annual growth that results. 
An immense amount of data on the abundance and the damage 
caused by the Gipsy Moth has been secured and will be prepared for a 
detailed publication later. The foregoing is only a brief outline of some 
of the methods used. 
THE USE OF BIOMETRICAL METHODS IN THE 
INTERPRETATION OF CODLING MOTH EXPERIMENTS 
By F. Z. Hartzell, Vineyard Laboratory , Fredonia, N. Y. 
Abstract 
In this paper, the use of statistical methods in the analysis of data of codling moth,.. 
Carpocapsa pomonella Linn., experiments and the manner of determining the degree 
of confidence that can be placed in the results are described. The importance of 
defining the region to which the results of the field tests apply, of selecting typical: 
