34 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
the uniformity found in this illustration it would be possible to analyze 
the data and determine mathematically the effect of the disturbing 
factor. We will omit the 
mathematical phases in this 
paper. However, in map¬ 
ping insect injury, if the 
center from which the in¬ 
sects spread can be ascer¬ 
tained, the use of concentric 
circles (or sectors of such 
circles) about this area if 
added to the map will indi¬ 
cate the divergence from 
uniformity. 
Mapping the Area 
In this phase of the prob¬ 
lem, we adopt the principles 
of topographic surveying, the 
only difference in field work 
being in vertical control. 
The first step is to divide 
the infested area into small 
subdivisions, preferably 
squares, and to make a map 
of the same. The most prac¬ 
tical instrument for this use is a small traverse plane table with com¬ 
pass and alidade. In horizontal control, the methods of locating 
points are those used in plane table surveying, the details of which are 
given in works on this subject. In surveying, vertical control consists 
in ascertaining the elevation of primary stations, traverse stations and 
selected points in the area surveyed, the instruments used being the 
level or aneroid barometer. Vertical control in mapping insect injury 
consists in determining the average amount of injury for each subdi¬ 
vision of the infested area and assuming this average to be located at 
the center of the subdivision. The method of ascertaining the amount 
of injury will be determined by the nature of the feeding, the degree 
of precision desired and the speed required. This demands that each 
investigator must formulate his own methods. The speed required 
should be determined first. It is essential that the injured area be 
mapped before any marked changes occur which might tend to oblit¬ 
erate the injury to be determined. Perhaps the most important 
changes will be produced by the growth or death of the plants infested 
