APPENDIX. 371 



DESCRIPTION OF SCALE AND INSECT. 



Sade of female — The scale of the female is circular, very slightly raised 

 centrally, and varies in diameter from one to two millimeters, averaging 

 about one and four-tenths millimeters. The exuvia? is central or nearly so. 

 The large, Avell-developed scales are gi'ay, excepting the central part cover- 

 ing the exuviae which varies from pale to reddish yellow, although in some 

 cases dark colored. The scale is usually smooth exteriorly or sometimes 

 slightly annulated, and the limits of the larval scale are always plainly 

 marked. The natural color of the scale is frequently obscured by the pres- 

 ence of the sooty fungus {Fumago salicina). 



Scdle of male — The mature male scale is oblong oval, nearly twice as long 

 as wide, and averaging in length about half the diameter of the female scale. 

 The position of the larval scale is marked by a nipple-like prominence located 

 between the center and the anterior margin of the scale. The scale of the 

 male is usually darker than of the female, sometimes black, but often gray, 

 the larval scale covering the exuvia? very frequently light yellow as with 

 the female. Not uncommonly the circular scale, formed prior to the first 

 molt, is black, while the later additions, giving it its oblong shape, are gray. 

 Eyg — The egg is never (or rarely) extruded as such by the female, and as 

 it exists within the body of the mother is a mere amniotic membrane, and 

 the forming embryo showing through gives it a yellowish white color. The 

 embryo with the envelope measures about two-tenths of a millimeter long- 

 by one-tenth of a millimeter wide. 



Newly hatched larva — The young larvse of both sexes are alike, and are 

 pale orange in color, with long oval bodies. They measure in length about 

 twenty-four hundredths of a millimeter by one-tenth of a millimeter in 

 width. The sucking bristles are normally doubled on themselves, but when 

 unfolded are nearly three times the length of the body. The antennaa are 

 apparently five-jointed, the last two joints being much longer than the 

 others, slender, subequal in length, and both finely and distinctly annulated. 

 The last joint bears a small nipple-like joint near the tip. The head is 

 somewhat concave in front, and the eyes are nearly transparent and slightly 

 purplish. .The terminal segment of the abdomen foreshadows in structure 

 the plates and spines of the adult female. The large central plates each 

 terminate in a long hair. The tarsus is represented by apparently a single, 

 strong, slightly curved claw. The tip of the tibia bears exteriorly two 

 rather long capitate hairs, and two similar hairs project also from the inner 

 extremity. Other details of structure are shown in the illustration. 



Larva of the seamd stage — After the first molt the difference in the sexes 

 becomes apisarent, although the covering scales are still identical. 



The female insects are somewhat smaller than the males at this stage. 

 The eyes, legs, and antenna? in this sex have entirely disappeared. The 

 form is almost circular, flattened. The color is yellow with irregular trans- 

 parent spots appearing in different parts of the body. 



The males are somewhat larger than the females, elongate, pyriform. 

 The eyes are prominent, purple in color. The legs and antenuai, as with 

 the females, are wanting. The general color of the body is yellow, with the 



