36 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
percentage of injury of each vine in the vineyard. After studying the 
map we tried various forms of graphic representation but found nothing 
better than the topographic chart to show the variation in injury in 
different portions of the planting. We divided the vineyard, as far as 
Fig. 2. Isofagal map showing the percentage of injury to grape buds by Haltica 
chalybea. Isofags shown by solid lines. Contours showing elevations in vineyard 
represented by broken lines. 
possible, into squares containing 16 vines each (four vines on a side), 
calculated the average injury in each square and located this average 
at its center. With the elevation (percentage of injury) and location 
of each point on the map, the contour points were found by interpola¬ 
tion and the contour lines drawn. The result is shown in Figure 2. 
