APPENDIX. 365 



The emergence of the young from the female over a period of six weeks 

 leads to a very confusing intermingling of generations and renders it diffi- 

 cult to make observations on the life-history except by isolating and watch- 

 ing individuals. By means of such isolation of individuals, however, we 

 have been able to most carefully trace the different generations. The course 

 of the development of a single generation follows : 



After being expelled the larva remains motionless for a little while, with 

 antennae and legs folded beneath the body. It soon hardens enough to run 

 about, and forcing its way out from beneath the protecting scale of the 

 mother, scurries over the plant to find a suitable place to settle. 



The newly born larva (Fig. 3, a) is an almost microscopic creature of pale 

 orange-yellow color, with long oval body, and with the customary six legs 

 and two feelers. The long thread-like proboscis with which the juices of 

 the plant are sucked up is doubled on itself and lies in an invagination of 

 the body wall, the tip only projecting. 



After crawling about for a few hours, the young larva settles down and 

 slowly works its long bristle-like sucking beak through the bark, folds its 

 antenna; and legs beneath its body and contracts to a nearly circular form. 

 The development of the scale begins even before the larva becomes fixed. 

 The secretion starts in the form of very minute white fibrous waxy fila- 

 ments, which spring from all parts of the body and rapidly become more 

 numerous and dense (Fig. lib.c). At first the orange color of the larva 

 shows through the thickening downy white envelope, but within two days 

 the insect becomes entirely concealed by the white or pale grayish yellow 

 shell or scale, which now has a prominent central nipple (Fig. 3. d), the 

 younger ones often possessing instead a central tuft. The scale is formed 

 by the slow matting and melting together of the filaments of wax. During 

 the first day the scale appears lil<:e a very microscopic downy hemisphere. 

 The matting of the secretion continues until the appearance of down and 

 individual filaments is entirely lost and the surface becomes smooth. In the 

 early history of the scale it maintains its pale whitish or grayish yellow 

 color, turning gradually darker gi^ay, the central nipple remaining lighter 

 colored usually throughout development. 



The male and female scales are exactly similar in size, color, and shape 

 until after the first molt, which occurs twelve days after the emergence of 

 the larva. With this molt, however, the insects beneath the scale lose all 

 resemblance to each other. The males (Fig. 4, a) are rather larger than the 

 females, and have large purple eyes, while the females have lost their eyes 

 entirely. The legs and antennse have disappeared in both sexes. The males 

 are elongate and pyriform, while the females are almost circular, amounting 

 practically to a flattened sac with indistinct segmentation, and without 

 organs, except a long sucking bristle springing from near the center be- 

 neath. The color of both sexes is light lemon yellow. The scales at this 

 time have a decidedly grayish tint, overcast somewhat with yellow. 



Eighteen days from birth the males change to the first pupal condition 

 (pro-pupa), (Fig. 4, b) and the male scales assume an elongate oval, sometimes 

 slightly curved shape, characteristic of the sex, the exuvia or cast larval 

 skin showing near the anterior end. 



