WALNUT APHIDES IN CALIFORNIA. 5 
the stem-mother; newly hatched young (fig. 2). 
Oval, lemon yellow. Eyes red, of moderate size. Antennae 3-jointed, not quite 
reaching to base of second coxae; joint III nearly three times as long as joints I and II 
together. Legs comparatively long, entirely pale. Body covered with capitate 
hairs. Cornicles very small, pale whitish -yellow, hardly raised above the surface of 
the body. Cauda small, pale, bluntly conical. Beak entirely pale, reaching second 
coxae. Black knee spots characteristic of this species absent. Measurements: Length 
of body, 0.72 mm.; width, 0.30 mm.; antenna, joint I, 0.04 mm.; joint II, 0.035 mm.- 
joint III, 0.145 mm. Almost immediately after birth the legs and antennae turn 
dusky gray and the dark abdominal spots appear. In 
this respect the young of the stem-mothers differ from 
those of all other generations, for the appendages of the 
young aphides of subsequent broods never turn entirely 
dusky nor do the abdominal spots appear so early. 
THE STEM-MOTHER; 4 DAYS OLD. 
Yellowish -green, flatly oval, closely appressed to the 
surface of the leaflet or bud scale. Antennae and legs 
dusky gray. Eyes circular, red, small. Head, thorax, 
two proximal antennal joints, and abdomen bearing capi- 
tate hairs which arise (those of the antennae excepted) 
from small tubercules situated in the middle of a small, FlG - 2 '~ C]l rom a ^ his W- 
. ,. . , _ . . , , ,. 1 . J i.., landicola: Stern-mother, newly 
circular, dusky area. Antennae 3-jomted, the distal joint etched (Original ) 
the largest. Cornicles very small, erect. Cauda almost as 
long as the hind tarsus, its apex blunt. Cornicles and cauda concolorous with the 
abdomen. Beak very pale, reaching second coxae, its extreme apex brown. Under- 
side of the head very pale yellow; of the abdomen greenish-yellow. 
the stem-mother; after first molt and just previous to SECOND MOLT. 
Pale lemon-yellow or yellowish green, flatly oval, closely appressed to the plant 
surface, occurring on the underside of the expanding leaves, between the ribs. 
Antennae and legs very pale yellow, almost hyaline. Antennae short, reaching slightly 
beyond the posterior margin of the prothorax, 3-jointed, with a rudimentary suture 
on the distal half of joint III. This joint is about three times as long as the two proxi- 
mal joints together. Eyes crimson, not fully developed. Legs entirely pale, with- 
out any trace of dark knee spots. Thorax and segments 1 to 6 of the abdomen with two 
longitudinal rows of black or brown spots, on each of which occurs a small pale tubercle 
bearing two capitate hairs, one larger than the other. On the thoracic segments and 
on abdominal segments 1 to 7 occur two rows of pale lateral tubercles, each of which 
bears three capitate hairs. The frontal margin of the head bears six such hairs on 
tubercles. Antennal joints I and II with a capitate hair on their inner margins near 
the middle, and joint III with one such hair on the inner margin near the base. The 
eighth abdominal segment bears a dorsal fringe of six capitate hairs, those on either 
end being smaller than the four inner ones. Cornicles situated on segment 6, as broad 
as long, erect, concolorous with the abdomen. Cauda without armature, bluntly coni- 
cal, almost hyaline, about as long as the hind tarsus. Beak barely reaching second 
coxae, pale yellow, the extreme tip brown. Measurements: Length of body, 1.55 mm. ; 
width, 0.775 mm.; antenna, joint I, 0. 053 mm.; joint II, 0.048 mm.; joint III, 0.304 
mm. 
Described from specimens collected at San Jose, Cal. ; March 28, 
1912. 
