12 Thomas Albert Williams 



Specimens in collection of the University of Nebraska (no. 8) 

 and of the U. S. National Museum (no. 125). 



8. Pemphigus populi-transversus Riley. 



Riley, Bull. U. S. Geol. Sur. Ter., Vol. V, I, p. 15, pi. fig. 5 (1879). 

 Thomas, Ins. 111., 8th Rep., p. 208, fig. 47 (1879). 

 Oestlund, Syn. Aph. Minn., p. 21 (1887). 



Winged female: Expanse 7 mm., pruinescent, with abdomen more yel- 

 lowish, inclining to green. Antennae reaching a little beyond the base of 

 front wings, smooth; III, IV and V cylindrical and of equal thickness; 

 III as long as the other two together; VI more slender at base and with 

 the apical unguis nearly as long as III. Thorax with mesonotal swellings 

 small. Terminal distance between first and second discoidal veins nearly 

 equal to that between this last and the stigmal vein ; discoidals almost 

 connected, cubital obsolete at base, subcostal heavy. Stigma scarcely wider 

 than subcostal space, acuminate at tip and with the vein starting a little 

 in front of its middle. Hind wings with the discoidals connected at base, 

 where the subcostal is slightly produced. Legs normal. Abdomen show- 

 ing about 30 pseudova and with 4 rows of faint piliferous dots on the 

 dorsum. 



Pupa with I, II, IV and V of antennae subequal in length. The wing- 

 less forms are pale creamy white, with faintly dusky members. 



Gall formed upon the leaf of Populus balsamifera. An elon- 

 gate oval swelling, causing the curving and broadening of the 

 petiole, and opening on the opposite side by a transverse slit, with 

 a whitish, slightly thickened and elevated margin, recalling human 

 lips. By the latter part of June the stem-mother is surrounded 

 with young of various sizes, all covered with the usual white 

 secretion, and mixed with the liquid globules. Winged females 

 produced in autumn, sometimes not till the leaves have fallen 

 (Riley). 



On cotton wood {Populus monilifera) . Lincoln, October 13, 

 1888, when winged females were found; Weeping Water, during 

 the summer and fall, 1888 to 1890; Ashland, June 20 and Septem- 

 ber 25, at which latter date winged females were found in the 

 galls, evidently but lately transformed. 



Specimens in collection of the U. S. National Museum (nos. 

 126, 128). 



96 



