WALNUT APHIDES IN CALIFORNIA. 
21 
individuals of this generation of which the date of deposition had 
been ascertained. Individuals of the fourth generation probably 
mature in an average of 16 days. The leaves of the Eastern black 
walnut fall earlier than those of the European or California black 
types, and consequently the viviparous aphides are not found so late 
on the trees. There are probably not more than nine generations of 
these in a year. 
Immediately after passing the final molt the aphides begin depos- 
iting young. These are entirely pale lemon-yellow with red eyes 
and four longitudinal rows of capitate hairs and do not exceed 0.70 
mm. in length. From 10 to 20 young are produced by a single female, 
dependent on the season of the year. The earlier generations are 
more prolific. After midsummer the progeny becomes smaller and 
smaller with successive broods. 
THE PUPA OF THE WINGED VIVIPAROUS FEMALE (FIG. 9). 
After the second molt the pupal wing pads are apparent as small 
emarginations on the sides of 
the thorax, but after the fol- 
lowing molt they are much 
more readily seen. The pupa 
of the winged viviparous female 
may be described as follows : 
Color generally pale lemon-yellow, 
sometimes white; head often with a 
reddish tinge. Antennas on small 
frontal tubercles, pale yellow, with 
the filament and articulations of joints 
3 to 6 dusky black. Eyes bright red. 
Thoracic segments and wing pads 
light yellow, wing pads projecting 
out from the body at a very acute 
angle. Legs pale, tarsal apices dusky. 
Body beset with long capitate spines 
in four rows. Cornicles on segment 6 
of the abdomen, hardly perceptible, 
broader than long. Cauda blunt, 
conical, and short. Cornicles and cauda concolorous with the abdomen. Beak 
pale, reaching to the middle coxae. Measurements: Length of body (average), 1.87 
mm.; width of body (average), 0.71 mm.; antenna, joint I, 0.058 mm.; joint II, 0.050 
mm.; joint III, 0.287 mm.; joint IV, 0.207 mm.; joint V, 0.201 mm.; joint VI, 0.128 
mm.; filament, 0.136 mm. 
This pupa is distinguishable from that of Chromaphis by the pres- 
ence of the dorsal rows of spines and by the absence of the black 
femoral spots. The penultimate instar occupies on the average four 
or Rve days. At its termination the final molt occurs, and after this 
the insect has acquired its full development. 
Fig. 
. — Monellia caryse: 
female. 
Pupa of winged 
(Original.) 
viviparous 
