712 Pomona College Journal of Entomology 



At tlic date of collection, June 22, 191 1, tliere was to be found in every 

 globular gall a single stem-mother wliich was giving or liad given birth to great 

 numbers of tlie winged viviparous females. Tliat this stem-mother produced 

 the original gall is without doubt, for though great numbers of the winged forms 

 have been eontinually leaving tlie galls, no new ones are being formed without 

 containing a stem-mother. Eitiier the stem-motliers are produced as a very late 

 brood or tliey arise from eggs wiiieli are deposited by the late broods. The latter 

 idea lias been lield by writers in tlie past and is more probable tlian the first, 

 though in this state it is almost impossible to find any of the Aphids laying eggs, 

 though they are known to do so in the Middle West and East. 



Hosts — This species occurs associated with and on the same branches of the 

 common Cottonwood {Populus trichocarpa T. & G.) as is Pemphigus populimon- 

 ilis Riley, though it is easily told by its characteristic galls (Figure 228). These 

 galls vary from the size of a large pea to a marble and are nearly globular in 

 shape. They are formed at the base of the leaf at the base of the midrib or stem. 

 The stem or midrib so twists as to form a semi-circular opening usually on the 

 underside of the leaf with the opening down, while the leaf tissues serve to cover 

 the twisted area so as to form a very perfect gall. So well is this made that 

 after examining great numbers of them there were to be found no parasitic guests 

 in the colonies and internal hymenopterous parasites could not be bred out of a 

 large number of collected galls. The color varies from a light green to a deep 

 bright red. The wall is thin so as to admit of a large space within. Figure 229 

 shows a cross section containing from Hftj' to two hundred individuals of all 

 stages. It is noticeable that the gall remains completely closed until the winged 

 forms are ready to emerge and then the opening is forced at a single point so as 

 to allow but one to leave at a time. The older galls, however, are opened clear 

 across. 



This species has also been reported as feeding upon Populus monilifera and 

 Populus treviuloides , by Eastern and Widdle Western writers. 



Localiiy — On the cottonwoods along the banks of the Santa Clara River 

 near Santa Paula, Cal. 



Date of Collection — June 22, 1J)11. Serial lumiber .'J9. 



Tribe CHAITOPHORINI 

 General Characters 



Bodi/ — Rather short, wide, flat, covered with fine hair-like bristles, which 

 are often jilaced on quite large tubercles, especially in the young. 



Antennae — Si.\ articled, except in one genus (Sipha), which has but five 

 articles, short, seldom longer than the body. Not on prominent frontal tubercles. 

 Covered with hair-like bristles same as the body. Usually carried at right angles 

 to the main axis of the body or against the sides (especially so in feeding). 



Lesrs — Short and rather stout, iiairv. 



Wing venation, as in Aphidini, veins sometimes with clouded borders. 



Cornicles — Short, truncate, variable in length, and not longer than one-tenth 

 the length of the body. 



