256 INSECTS 



yellow spots, turning white later, and often killing the 

 tops. This the experienced grower will recognize as 

 the work of Thrips, which scrape the surface so as to 

 break the leaf-cells and exhaust the sap, leaving a dead 

 spot. When these dead spots become sufficiently 

 numerous, the leaf fails to fulfil its function and dies, or 

 is only a burden to the plant. 



Leaf- and tree-hoppers do similar work and a com- 

 mon example is found in the vineyard, where leaves 

 often turn brown in summer before the fruit is ripe, 

 because of the injuries done by the grape leaf-hopper. 



Scales, soft .and armored, attack trees of all kinds, 

 in the orchards, in the forests and on the city streets. 

 Sometimes they are so small and inconspicuous that it 

 requires close scrutiny to find an isolated individual; 

 sometimes they are large and showy, flaunting their 

 numbers and threats as far as the tree itself is clearly 

 visible. The honey-dew and soot fungus produced by 

 the soft scales have been already referred to. Many of 

 the armored scales produce a specific effect on the tree, 

 besides exhausting its juices. In some cases distinct 

 pits or depressions are formed on the surface of the bark ; 

 in others the bast is discolored and poisoned where the 

 puncture is made, and when the punctures are suffi- 

 ciently numerous the bast simply fails to do its work. 

 Peach trees infested by the San Jose scale sometimes 

 reach such a condition in fall that, after growth is 

 completed, the bast has lost all vitality. During the 

 winter the poison does its work; in spring the tree 

 starts from the supply stored in the buds, blossoms 

 and even begins to leaf out, but when demand is then 

 made upon the roots for fresh nourishment the bast 

 fails and the tree dies. 



This poisoning effect is not peculiar to scales, but 

 is a feature in many other of the Hemiptera. Some of 



