THE MUSSEL-SCALE OF THE APPLE-TREE 165 



be remarked as a singular exception to the absence of a 

 resting-stage in Hemiptera, that the male scale-insects, but 

 not the females, undergo complete transformation. The 

 female often produces eggs in early winter, but sometimes not 

 till the new year ; she lays from twenty to thirty, and then 

 dies, the eggs remaining protected by her dead body and 

 shield. 



In spite of the biological interest of this curious life-history, 

 the cultivator immediately asks how the insect can be most 

 readily destroyed. When the branches to which the mussel- 

 scales cling are strong enough to bear rough handling, scraping 

 or rubbing briskly with coarse sacking will be effective. This 

 is best done in winter, and may be followed up by washing 

 thoroughly with soap and carbolic acid, or soap and petroleum 

 (see American blight). In May the boughs should be washed 

 again with the solution, to kill the insects before they have 

 firmly established themselves. Coccidse are preyed upon by 

 beetles, lace-winged flies, and Hymenopterous parasites. Mr 

 Newstead finds that the stomachs of titmice often contain the 

 mussel and other scale-insects 



The oyster-scale (Aspidiotus ostreiformis) of the apple and 

 other fruit-trees, which occurs also on lime, willow, and poplar, 

 is densely crowded, like the mussel-scale. The shield is 

 circular, slightly convex, and when magnified shows yellow 

 prominences on a dark grey ground ; it consists of one or 

 more cast skins, and the waxen exudation. The shield is 

 easily separated from the body of the animal, which is yellow, 

 and nearly circular in shape. The male scale, which is of 

 frequent occurrence in this species, is not circular, but oval. 

 The life-history is similar to that of the mussel-scale. 



Currants of all kinds and gooseberries are often infested 

 by a scale-insect of another group, in which the shield consists 

 merely of the living or dead body of the parent, with a waxen 

 exudation enveloping the eggs, but not forming part of the 

 shield. The shield is much larger than in the mussel or oyster- 

 scale, and nearly hemispherical. Such scales as these often 

 belong to scale-insects called Lecanium ; the currant-scale is 

 Lecanium ribis. A woolly scale (Pulvinaria) also attacks 

 currants. 



