80 
in size the dark-colored exterior central portion of the scale. The ~ 
ventral scale is insignificant. 
Male scale.—The seale of the male is elongate oval, having a length 
of about 1mm. The exuvia is near one end, and as a rule exposed. © 
It is unusual to find the scale of this cee entirely free from extra- 
neous matter, and it adheres so closely to the bark that invariably any 
loose vegetable fibers or adhering foreign matter is lifted and carried 
over the surface of the scale so that the latter is often obscured by sooty 
fungus, dirt, or the epithelial cells of the bark. On young twigs the 
hyaline epithelial layer of the bark is raised and adheres to the scale, 
Fig. 3.—Aspidiotus ostreeformis: a, adult maleinsect; b, adult female; both 
much enlarged (original). 
giving it a uniform grayish tint throughout, and making it almost 
impossible to determine, without dissection, the limits of the scale. 
On wood infested for two or three years, the scale often exhibits a raised 
or puffed appearance, due partly to the constant elevation of the old 
scales by the new ones forming beneath them and the disintegrating 
action of moisture, and also to the action of various saprophytic and 
perhaps parasitic fungi. 
The larval seale is yellowish-white, and occurs in clusters under the 
old female, and also on all free bark adjoining. 
DESCRIPTION OF THE ADULT FEMALE INSECT. 
The adult female is a rather larger insect than any one of its near allies, 
except A. juglans-regic. It often attains a diameter of 14 mm., and is 
nearly circular, the anal plate in spent females being, however, slightly 
retracted, giving the insect a slightly kidney-shaped appearance. The 
female is quite flat, even when in the gravid condition, a form necessi- 
tated by the nature of the covering scale. (Fig. 4.) 
The terminal segment or anal plate has the following peculiarities: The 
lateral groups of the paragenital glands are arranged in rather circular 
