THE HOMOPTERA 209 



conditions, this results in the death of the plant they are on. A few are 

 beneficial to man. Thus the bodies of a scale feeding upon cactus, when 

 dried and prepared, furnish the dye known as Cochineal. Shellac is 

 obtained from the excretions produced by another scale, and China wax, 

 used as furniture polish, comes from a third species. Most scale insects, 

 however, are injurious and fail to compensate for the injury they cause by 

 producing anything of value. 



Among so many serious pests, only a few can be considered in detail 

 here. Taking the armored scales first, these are the Oyster shell, the 

 Scurfy and the San Jose Scales, with brief reference to a few others. 



Armored Scales 



The Oyster-shell Scale (Lepidosaphes ulmi L.). This insect, native 

 to Europe, has been so long in this country that it is now very generally 

 distributed. It is chiefly an enemy of the apple, pear, poplar, willow, 

 ash and lilac, but is often found on other plants. It feeds on all parts 

 covered by bark, and the male scales are also often found on the leaves. 



FIG. 203. Female scales of the Oyster-shell Scale (Lepidosaphes ulmi L.) on a twig, about 

 twice natural size. (Original.) 



The full-grown female scale (Fig. 203) is about one-eighth of an inch 

 long and has much the form of an oyster shell, one end narrowly rounded, 

 the other rather more broadly so, and the shell as a whole usually bent 

 somewhat to one side. It is brown to gray in color, varying with age, 

 and to some extent, the plant it is on. During the winter examination 

 of the scale will show beneath it at the narrower end, the dead body of the 

 insect, and behind it from 15 to 100 tiny whitish eggs. These hatch the 

 following May or June, according to the advancement of the season, into 

 very small whitish nymphs or ''crawling young," which are extremely 

 delicate and with no scale. These young crawl out from beneath the 

 parent scale and wander about for a few hours or even a day or so, seeking 

 for places where they may settle: then each thrusts its beak through 

 the bark and begins feeding, and degeneration of eyes, antennae and 

 limbs, and the secretion of wax over the body begins. To this secretion 

 the molted skin is added at each molt, making a very tough, hard, cover- 



14 



