14 



twigs and small branches, and locate there permanently. In a day or 

 two they begin the formation of the scale. The male scale is much 

 smaller than the female, elongate, wider behind than in front, and 

 little, if any, curved. It is uncommon on apple, but often found on 

 other food plants. The winged male insect appears in midsummer. 

 There is but one brood a year in the North, but in parts of the South 

 there are apparently two broods; the second one hatching about Sep- 

 tember 1. The oyster-shell bark-louse is widely distributed and 

 attacks a great variety of trees, but is especially partial to apple. 



THE SCURFY BAKK-LOUSE. 



{Chionaspis furfurus Fitch — flg. 4.) 



This common orchard scale is readily known by its whitish color and 

 ovate form. The adult female scale is rather flat, irregularly ovate in 

 outline, with the yellowish exuvium at the apex. The life history is 



similar to that of the oyster-shell 

 bark-louse. The eggs are laid in 

 the early fall and occupy the 

 greater part of the scale. The 

 mother dies and the scale re- 

 mains on the tree during the 

 winter to protect the eggs. The 

 young hatch during the latter 

 part of May or early in June. 

 The male scale, which is often 

 very abundant, is much smaller 

 than the female, snow-white in 

 color, and fully twice as long as 

 broad, with nearly parallel sides 



Fig. i.—CUonaspis fiirfurus: a, b, infested twigs; c, j iu i i • j mi 



female; d, male. (Howard.) ^^^ ^'^^^^ «;eels Or ridgeS. The 



winged male insects issue in Sep- 

 tember. There is but one brood in the North, but probably two or 

 even three in the South. The scurfy bark-louse is widely distributed 

 and occurs on most orchard trees, but chiefly on apple and pear. 



AspiDioTus (Circular or Round Scales). 



To this genus belongs the most destructive known species, the San 

 Jose scale. The other species, however, often cause much damage. 

 There is a considerable resemblance among the various species, so 

 that it is difficult for any inexperienced person to determine them. 

 The final characters that separate species are based on the structure of 

 the pygidial plate of the adult female scale. To observe this it is 

 necessary that a specimen be boiled in caustic potash and mounted in 

 balsam on a glass slide. When this is examined under a microscope 

 the lobes, spines, hairs, and sinuations of the margin of the plate 



