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 CaUipterini, 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 



