SCALE-INSECTS, BARK-LICE, MEALY-BUGS, 227 
insects, the ‘armored scales,’ to which the common and well- 
known oyster-shell bark louse of the apple belongs. It differs 
from this species and, in fact, from all other eastern species 
found upon deciduous fruit trees in that the scale is perfectly 
round or, at most, very slightly elongated or irregular. It is flat, — 
pressed close to the bark, resembles the bark of the twig in color 
and when fully grown is about one-eighth of an inch in diameter. 
Fig. 182.—Aspidiotus perniciosus Comst.: a. infested twig, natural size; b, bark 
as it appears under a hand lens, showing scales in various stages of develop- 
ment, anc young larve. From Div. of Entomology, Dep. of Agriculture. 
At or near the middle of each scale is a small, round, slightly 
elongated black point or this point may sometimes appear yel- 
lowish. Young and full-grown scales are shown in the illustra- 
tion, (Hie 182) b).. See also: Fig. 185; Plate XV. 
“When occurring upon the bark of the twigs or leaves and 
in large numbers, the scales lie close to each other, frequently 
overlapping, and are at such times difficult to distinguish with- 
