Pomona College Journal of Entomology 



705 



widtli O.'iO mm. Stif;m;il vein iiii(hil;itc, arising mar the tip of tlic stigma and 

 ratlitr sharply curved downward until near the middle, then curves upwardly 

 until near the tip where it turn down, curves well rounded and not at all abrupt, 

 lirown ; first discoid.al arising near tlie middle of the subcostal vein and extending 

 almost straight to the wing margin at an angle of nearly 15 degrees to it, usually 

 curves slightly inwjirdly towards the body; second discoidal rises near the base 

 of the first, and extends nearly ])arallel to the third discoidal, curves slightly 

 inwardly, much longer (nearly twice) tlian the first discoidal; third discoidal obso- 

 lete at base, nearly parallel with second discoidal but diverges towards the tip of 

 the wing, the tip is midway between tips of the stigmal and second discoidal; 

 veins brown or amber. Secondary — Length 3.2 mm., width 0.9 mm. ; subcostal 

 with two downward curves, one at the bases of the discoidals and the other two- 



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Figure 224. Pemphigus populimonilis Riley 



thirds its length ; discoidals arising at one-third the length of the sub-costal, 

 where it makes a rather sharp bend, from a rather narrow brown or amber spot, 

 their bases close together ; first discoidal curving towards the tip, while the sec- 

 ond curves toward the base of the wing; veins amber. Cauda — Well rounded and 

 inconspicuous. 



Nymphs — The nymjihs of the winged viviparous females are often very large 

 before their wings are fully developed. The color varies from a light yellowish 

 to a dusky green. The head is usually darker. The entire body is covered with 

 a very fine white powder and there is no sign of flocculence until the adult stage 

 is reached. 



APTEROUS VIVIPAROUS FEMALES 



A])]iarently there are no apterous forms occurring in the galls observed in 

 this locality. 



Hosts — Infesting the common Cottonwood {Popiilits trichocarpa T. & G), 

 forming rows of the bead-like galls on the leaves. The galls are formed more 



