984 
Journal of Agricultural Research 
Vol. V, No. 21 
It will be noted that in general the smaller forms occurred earlier in 
the year than the large ones, at a time when the average length of the 
nymphal period was particularly short; also that, while the percentage 
of young produced by the larger insects is below the seasonal average, 
it is, on the whole, higher than the average of the period in which the 
insects occurred. 
It is very difficult to judge exactly the condition of the food supplied 
to the insects. The size of the leaves furnishes no criterion as to the 
amount of food available. The aphides do as well on young, newly 
opening leaves as on larger ones. In fact the largest, plumpest aphides 
reared were fed on such foliage, while the poorest conditioned insects 
were raised on old, dark leaves, whose general condition can perhaps 
best be described as “hard.” 
Some of the dormant trees used in the spring continued to live through¬ 
out the season. These furnished very satisfactory food at first. They 
put out slender twigs which never hardened and the leaves of which 
never fully unfolded. During the latter part of the summer, while the 
foliage continued perfectly green and appeared to be very succulent 
growth practically ceased. Aphides confined on these plants grew 
slowly and never attained the size or plump condition of the average 
adult. 
SEXES 
OVIPAROUS FEMALE (PI,. EXVII, FIG. 4) 
DESCRIPTION 
First instar. —Morphological characters: Antennae as follows: I, 0.025 mm.; II, 
0.032 mm.; Ill, 0.096 to 0.128 mm,; IV, base 0.042 to 0.056 mm., unguis 0.088 to 0.12 
mm.; segments I and II with stout spinelike hairs, III and IV imbricated and bearing 
similar spines; segment III with a distal sensorium, and IV with the usual sensory 
group. Compound eye with about 14 facets. Labium about as long as the antennae. 
Legs hairy, hind tibiae about 0.209 mm ‘ long. 
Color characters: Very variable, usually an olive green, with dusky appendages. 
Second instar. —Morphological characters: Antennae as follows: I, 0.028 to 0.042 
mm.; II, 0.028 to 0.042 mm.; Ill, 0.06 to 0.112 mm.; IV, 0.048 to 0.08 mm.; V, base 
0.058 to 0.08 mm., unguis 0.12 to o. 16 mm.; segment IV with a distal sensorium, and 
V with the usual sensory group, otherwise quite similar to antennae of last instar. 
Compound eyes with about 24 facets. Labium nearly as long as III and IV of the 
antennae. Cornicles thick, rounded at the tip. Legs more slender than in the pre¬ 
vious instar; length of hind tibiae, 0.256 to 0.32 mm. 
Third instar. —Morphological characters: Antennae as follows: I, 0.048 mm.; 
II, 0.048 mm.; Ill, 0.16 to 0.176 mm.; IV, 0.109mm.; V, base0.08mm., unguis0.184 
to 0.208 mm.; segments armed similarly to those of the previous instar. Compound 
eyes with many facets. Cornicles more cylindric than in the previous instars, 0.112 
mm. long. Legs slender, hind tibiae 0.112 mm. long. 
Color characters: As in previous instars. 
Fourth instar. —Morphological characters: Antennae as follows: I, 0.048 mm.; 
11,0.048 mm.; Ill, 0.096 to 0.16 mm.; IV, 0.08 to 0.152 mm.; V, 0.096 to 0.144 mm.; 
