February, ’18] 
HARTZELL: GRAPHIC ILLUSTRATION 
37 
We have also indicated the elevation of various parts of the vineyard 
by means of contours with broken lines. 
From the map we note the following: (1) the distribution of injury 
is irregular; (2) the most extensive destruction of buds occurred in the 
southwestern portion of the vineyard; (3) the west side of the area 
was more severely injured than the east side; (4) the greatest varia¬ 
tion in the percentage of injury was on the south side; (5) taking the 
vineyard as a whole, the edges show a higher destruction of buds than 
portions of the area slightly nearer the center; (6) peaks (portions 
having greater injury than the surrounding areas) and depressions 
without an outlet (portions having less injury than surrounding areas) 
are common. In this latter respect, our chart differs from the ordinary 
topographic map for, on land, depressions without an outlet are gen¬ 
erally filled with water and therefore depressions with closed contours 
are seldom shown. 
Regarding the causes of the infestation, we observe the following 
facts. The center of infestation was in waste land southwest of the 
vineyard. The beetles fly with the wind and are not active at tem¬ 
peratures below 55° F. and, on the days during May, 1914, when the 
temperature was above 55° the wind was from the south or southwest. 
In the vineyard, the movement of the beetles was in the direction of 
the prevailing wind on the warmer days. The beetles appear to be 
decidedly adverse to flying in any direction which has an angle of more 
than 45° to the direction of the prevailing wind. There appears to be 
no marked correlation between the topography of the vineyard and the 
distribution of insect injury, although it is to be noted that the infesta¬ 
tion was light on the highest portion of the ridge. The woodland west 
of the vineyard shielded a portion of the area from the cold north and 
northwest winds, and, as the portion of the area nearest the forest was 
warmest, we believe the beetles were attracted to this section in greater 
numbers than elsewhere which accounts for the serious injury on this 
side of the vineyard. The increased injury near the northern and 
eastern edges may perhaps be explained by the fact that the vineyard 
was isolated and also that the beetles fly only from vine to vine. 
Hence, when they came to the edges of the vineyard, not finding vines 
beyond, they remained, and others continuing to arrive formed an 
accumulation of beetles which produced a greater percentage of injury 
than is found on the vines slightly farther removed from the edges of 
the vineyard. 
A Cardboard Model 
In an intricate chart like the one shown in Figure 2, it may be diffi¬ 
cult to visualize the relative differences in elevation especially when 
peaks and closed depressions occur near each other. To overcome 
