149 
mii the escape of the mature insects, d andje. Incipient double galls, one being located 
on each side of the mid-rib. /, The wingless female, with the cottony secretion attached, 
g, The winged insect. The marks at the sides of g and / indicate the natural size. 
Pemphigus populicaulis, Fitch. The Poplar-leaf Gall-louse. 
This species forms the swellings or galls about the size of a bullet, 
so often seen on the leaves of the cotton-wood (Populus monilifera) 
at the point where the blade joins the stock or petiole.. These galls 
often assume a reddish tint, and sometimes grow to the size of a small 
marble; having a mouth-like orifice on the under side and a cavity 
within where the lice reside. As Dr. L. Baron, has given an account 
of this species in his Third Report, it is unnecessary for me to notice 
it further than to give a description of the species, which is omitted 
in that report. 
The galls usually begin to appear early in May, and at first are oc¬ 
cupied by a single wingless female, which in midsummer becomes the 
mother of a numerous progeny, often amounting to one-hunered and 
fifty in number. Dr. L. Baron, is of the opinion, from some obser¬ 
vation he made, that they pass the winter in the egg state, and that 
the eggs are placed at the base of the buds. 
The young lice are of a pale greenish or whitish color, "variable 
in size, but usually about three-hundredths of an inch long. The wing¬ 
ed individuals make their appearance about the middle of June. These 
are of a blue black color throughout, sometimes with the base of the ab¬ 
domen and legs pale brown. While in the gall, the wings appear to 
rest horizontally on the back, but when they leave this they are held 
erect in repose, as is usual with tl e species of this genus; they aie 
whitish and not perfectly clear, being more or less dusted over, as is 
the body, with a white powder; the marginal vein is robust and blue- 
black from the base to the stigma, but slender beyond that point; the 
rib vein is also robust and of the same color till it reaches the stigma, 
where it is widened to twice its previous thickness, forming a broad 
blue-black margin along the inner side of the stigma; the stigma is 
dull white; discoidal veins, pale yellow; the first of these veins is 
straight, the second arises almost in contact with it, and is straight 
nearly to its tip, where it curves slightly toward the inner margin; the 
third vein obsolete for about one-fourth of its length at its biise. 
Length to the tip of the abdomen about one-tenth of an inch; to the 
tips of the wings, one-seventh of on inch. ^ 
Specimens sent to me by Mr. W. F. Bundy, oi Sauk C ity, \\ is., 
were found on the Aspen [Populus tremuloides ) and are probably the 
same as the above described. The following is the description taken 
from alcoholic specimens: 
Winged individual .—Front wings with the three simple branch 
veins very slender and pale, obsolete at the base; fouith vein cuives 
regularly and slightly at the base and before it reaches the apex le- 
curves; stigma rather short, acute angled at the base; posteiioi mai- 
gin rounded to the apex, dull yellowish or light brownish with a 
broad brown posterior or inner margin. Antenna 3 short scarcely readi¬ 
ng beyond the tip of the thorax, third joint as long or longer than 
