138 
examples the leaf is folded up around the gall forming a more or 
less complete rim. Many of the galls are produced above into 
nipple-shaped prominences. The color may be purple or pale green. 
A specimen measured was .083 inch in depth, and .065 inch in 
diameter. 
Phytoptus salicicola, n. sp. 
Produces galls on the leaves of the long-leaved willow, Salix 
longifolia, Muhl. 
s' 
Strhe of abdomen 46. Featlier-like tarsal appendage with three 
pairs of prongs. Length .0075 inch. Abundant in the galls in 
June. 
This gall is one of the most remarkable deformations I have 
seen. It consists of a narrow longitudinal upward fold extending 
sometimes the entire length of the leaf. Usually there are two of 
these folds on each leaf one on each side of the midrib. They 
may be close to the midrib, midway between it and the margin, or 
at the margin itself. In cases where the fold begins next the mid¬ 
rib at the base of the leaf, it may gradually leave it so as even¬ 
tually to form a mere fold of the margin. The opening is a narrow 
slit running along the under side of the leaf. Color, as seen in the 
hitter part of June, brown. My attention was drawn to this gall by 
the peculiar appearance of the willow leaves due to the lessening of 
their widths by the fold. A clump of shrubby willows growing in 
the margin of a shallow pool of water in the vicinity of Normal, 
Ill., was badly infested by the galls. 
Phytoptus querci, n. sp. 
Produces galls on the leaves of the bur-oak, Quercus macrocarpa , 
Miclix. 
The mite is long and slender, and in a specimen seen among 
washings from a cecidium, there appeared to be an abrupt descent 
in the outline of the back from the abdomen to the eephalothorax. 
Length .005 inch. 
The gall is large, greenish-yellow, entirely open below and slightly 
convex above. The hollow is densely filled with brown pubescence. 
The form is variable but the outline usually regular. The surface 
is smooth, or slightly roughened by the veinlets. Some of these 
galls grow downward instead of upward and form brown velvety but¬ 
tons on the under side of the leaves. Specimens measured were 
from .1 inch to .4 inch in diameter. Thirty galls have been counted 
on one leaf. This is a common gall in Northern Illinois and Indi¬ 
ana, and has been found occasionally in the central part of Illinois. 
Phytoptus thujce, n. sp. 
Occurs on the leaves of the American arbor vitae, Thuja occident¬ 
alism Linn, in summer, and in the buds and under the leaves ip 
winter. 
