8 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 
Cornicles (fig. 5, b) pale yellow, constricted in the middle, barely as long as broad. 
Abdominal segments 3 to 6 inclusive bearing pale lateral tubercles. Body without 
hairs. Cauda very pale, globular, about as long as the cornicles. Beak pale yellow, 
the extreme tip black, reaching a little beyond the first coxae. Sternum pale brown. 
Measurements: Length of body, 1.62-2.55 mm., average 2.08 mm.; width of body at 
segment 3 of abdomen, 0.71-1.06 mm., average 0.88 mm.; wing expanse, 4.42-5.21 
mm., average 4.77 mm.; antenna, joint I, 0.046-0.067 mm., average 0.055 mm.; joint 
II, 0.039-0.055 mm., average 0.043 mm.; joint III, 0.267-0.408 mm., average 0.337 
mm.; joint IV, 0.153-0.233 mm., average 0.196.mm.; joint V, 0.133-0.191 mm., aver- 
age 0.162 mm.; joint VI, 0.079-0.094 mm., average 0.083 mm.; antennal filament, 
0.038-0.043 mm., average 0.040 mm.; total length of antenna, 0.775-1.060 mm., aver- 
age 0.916 mm.; cornicles, 0.05 mm.; cauda, 0.056 mm. 
There are from 6 to 8 transverse oval sensoria on antennal joint III, 1 terminal sen- 
sorium on joint V, and three terminal ones on joint VI. Buckton's measurements 
(Buckton, 1872) seem to have been taken from small examples for, with the exception 
of those of the antennal joints, his measurements are all smaller than the average found 
by the writer. It may be that California examples are larger than the European. 
"Within a few hours after the last molt the wings harden and the chitin 
stiffens. The stem-mothers then begin to deposit the young that 
have been visible as pseudova for a week or longer inside their bodies. 
In the life-history experiments the greatest number of young pro- 
duced by one viviparous female was 44. These were extruded from 
the body in 20 days, 30 in the first half and 14 in the last half of that 
period. Several adults under observation deposited 11 or 12 young 
within 12 hours after reaching maturity, and no more after that, 
dying with many unborn pseudova in their bodies. In the field 
the aphides deposit all their young on one leaf or on several leaves 
near one another. The average number of young deposited by a single 
adult ranges between 25 and 35. This seems to be about the same as 
in other closely related Callipterini, but is a much smaller number 
than that occurring in members of other tribes of Aphididse. The 
aphides of the fall viviparous generation produce fewer young, 
those which develop in November depositing only 6 or 8. As many 
as 30 oval unborn aphides may be seen in the body of one recently 
molted female. These embryos vary in size, only those to be de- 
posited immediately being fully grown. Each is inclosed in a very 
thin hyaline sac in which they are contained at birth. 
The newly deposited young of the second and subsequent genera- 
tions, both viviparous and oviparous, differ from the infant stem- 
mothers in that they are entirely pale yellow (rarely suffused with a 
faint pink) and remain thus until the first molt, while the young 
stem-mothers have dusky appendages and abdominal spots. The 
young deposited by the stem-mothers pass through their first molt 
in from three to six days. After this molt there appear brown or 
black dorsal spots in the majority of the individuals, and these 
markings persist through the succeeding molts. A small percentage 
