HEMIPTERA: THE TRUE BUGS 



85 



than one sixteenth of an inch in diameter, having a dark 

 raised point near the center. At first these scales are 

 likely to be scattered here and there over the bark, but as 

 they increase in numbers, they are found nearer together, 

 touching or overlapping one another. Finally, when they 

 become very abundant, they make a thick scurfy layer, of 

 a grayish color that obscures the natural color of the bark 

 and is easily rubbed off with 

 a knife. The presence of 

 such a layer indicates that 

 the sap from the bark is be- 

 ing sucked out by millions 

 of the insects, and that the 

 health of the tree is being 

 seriously impaired. 



The young scales that live 

 thrpugh the winter develop 

 in early spring into mature 

 insects, and each of the fe- 

 males may give birth to about 

 four hundred young. These are tiny yellow creatures that 

 crawl around for about a day before they finally fasten 

 themselves to the bark by inserting their curious beaks to 

 suck the sap. They then begin to secrete the scale which 

 is so characteristic of this family of insects. The scale is 

 composed of white waxy threads secreted by the skin of 

 the larvae, which mat together to form a rather dense 

 covering. This whitish scale turns gray or even almost 

 black within a few days. The female scales are always 

 wingless, but the male scales develop into active two- winged 

 insects which are able to fly about. 



When the San Jose Scale appears upon older trees, it is 

 most likely to be found on tw^gs and smaller limbs, but 



BLACK SCALE 



