20 KANSAS UNIVERSITY SCIENCE BULLETIN. 



0.18 mm. broad and 0.81 mm. long. What appear to be sen- 

 soria are situated along the subcostal vein near the stigma. 

 An enlarged view of the same is shown at a, in the illustration. 

 Total wing expansion, 6.00 mm. Legs normal, with the ex- 

 ception of long tarsi, they being 0.25 mm. long. 



The abdomen is dark green or yellowish green after the cot- 

 tony secretion is removed. Honey-tubes and style obsolete. 

 Total length of the body, 1.82 mm. 



This form was taken June 21, on the ash {Fraxi aus americaims) . 

 It is gregarious, and colonizes the terminal leaves, which causes 

 them to curl and form a pseudogall that protects the lice. 



Pemphigus populicaulis Fitch. Plate VI, fig. 40. 



Apterous form. — Head black. Antennie black; length of 

 joints: I, 0.03 mm. ; II, 0.05 mm. ; 111,0.10 mm.; IV, 0.07 

 mm.; total length, 0.25 mm. Eyes black, the cornea, of which 

 there are three, resemble ocelli, and lie in the black pigment of 

 what corresponds to the eye. Beak black, 0.27 mm. long, ex- 

 tending midway between the pro- and mesocoxae. 



Thoracic divisions not differentiated from the remainder of 

 the segments. Legs black and short. 



Abdomen large and spherical, also pulverulent. Honey- 

 tubes and style obsolete. 



This form was taken May 17, in a cottonwood gall. This 

 gall is on the petiole at the base of the leaf. The interior of 

 the gall is smooth, and contains besides the exuvioe of the lice 

 several liquid globules coated with a pulverulent matter which 

 gives it the appearance of mercury in its behavior, since it re- 

 tains a globular form. All the insects in the gall, sometimes 

 numbering 500, have this same coating of pulverulent matter. 

 They are produced at the rate of about ten per day. Usually 

 there is but one viviparous mother in the colony, but sometimes 

 two are found. An illustration of the stem-mother is shown in 

 plate V, figure 34. These forms were taken July 17. The 

 adults are at this time leaving the galls, but they were not 

 found in any other place. Yet, under artificial conditions, they 

 were observed laying their eggs on apple twigs. 



Following is Mr. Burrows's description of the gall : "This 

 gall occurs throughout the summer on the petiole of the leaf of 

 the cottonwood {Populus monilifera) . The gall is a subglobu- 



