40 THE SAN JOSE SCALE. 
difficult to make observations on the life history except by isolating* 
and watching individuals. By means of such isolation of individuals, 
however, we have been able to most carefully trace the different genera- 
tions. 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 protect- 
ing scale of the mother, scurries over the plant 'to find a suitable place 
to settle. 
The newly born larva (fig. 3a) 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 antennae 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 filaments, which spring from all parts of the body 
and rapidly become more numerqus and dense (fig. 36, 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 promi- 
nent central nipple (fig. 3d!), 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 
like a very microscopic downy hemisphere. The matting' of the secre- 
tion 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 gray, 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. 4a) are rather larger 
than the females, and have large purple eyes, while the females have lost 
their eyes entirely. The legs and antennae have disappeared in both 
sexes. The males are elongate and pyriforin, 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 beneath. 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 condi- 
tion (pro-pupa), (fig. -lb) and the male scales assume an elongate oval, 
