180 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
the fruit of each tree in the sample is counted, cut open and the number 
of infested apples determined. While we are waiting for this determina¬ 
tion it is advisable that we all make similar counts no matter how ex¬ 
tensive. If but one tree is examined and we use all the fruit and count all 
the infestation, the data may be useful but if one worker counts but 5 
apples per tree or 100 apples picked at random from several trees, and 
another worker bases his figures on the relation of packing house culls to 
total crop the figures are practically incomparable. 
If a unit Hessian fly sample is to be 10 plants or a square yard it is 
advisable to have this unit established arbitrarily even though the 
necessary frequency is still under investigation. 
This symposium and the discussion will at least focus the attention of 
entomologists upon this most important phase of entomological work. 
Future observational work for statistical data will lack much of its 
potential value until we have a general realization of the importance of 
these factors. With their appreciation we should eventually be able to 
codify the necessary mass of data and the type of data necessary in 
estimating the abundance and damage for any of our more important 
insect pests. 
METHODS OF ESTIMATING ABUNDANCE AND DAMAGE 
CAUSED BY THE GIPSY MOTH 
By A. F. Burgess, Melrose Highlands, Mass. 
Abstract 
The methods of securing information on the abundance and damage caused by the 
gipsy moth, Porlhetria dispar Linn., are detailed for the purpose of indicating the 
means that can be used to secure information on a single brooded tree-defoliating 
insect. Detailed information was secured from different areas and in different types 
of forest growth. 
The abundance and destructiveness of any insect depends not only on 
the rate of increase but on the ability of the species to overcome such 
impediments as unfavorable climatic conditions, natural enemies and 
other retarding agencies. 
If all factors are properly balanced the insect exists but causes small 
economic loss. A pest such as the gipsy moth, Porthetria dispar Linn., 
is not perfectly adjusted to its environment either in this country or in 
its native home and a study of its increase under field conditions is of 
great importance. The methods used are doubtless somewhat original 
and may be found of value when similar studies are made on other pests. 
The eggs of the gipsy moth are deposited in a single cluster and can be 
