WALNUT APHIDES IN CALIFORNIA. 5 



the stem-mother; newly hatched young (pig. 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.; 

 ioint 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 - ^.-Chrom aphis jug- 

 , . , . , n • • J. i ii t j i ■ • landicola: Stem-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. 



