REPORT OF THE STATE ENTOMOLOGIST IQI7 65 
galls are upon two-year old wood, that is, that which grew the 
second season preceding. The individual galls in June are about 
three-sixteenths of an inch long with a diameter of one-sixteenth 
of an inch, plainly ribbed, greenish and moderately soft. At this 
time considerable sweetish fluid must be excreted, since badly 
infested trees are very attractive to insects, both bees and flies being 
present. 
If the oak club gall and the knotty oak gall are injurious to trees, 
it is very probable that this species is detrimental, especially when 
abundant and the infestation is allowed to continue for a series of 
years. It is very probable that the damage could be minimized to 
a considerable extent by judicious pruning and burning of the infested 
twigs in early summer prior to the galls maturing and dropping 
from the twigs. 
Linden bark gall (Agromyza tiliae Coud.). Twigs of 
American linden infested with this insect were received April 21, 
1917, from Dr Hermann von Schrenk, St Louis, Mo., accompanied 
by the statement that the gall fly was abundant and seriously 
injurious to lindens at Kirkwood. Badly infested twigs, he stated, 
break off after a time, evidently because the circulation of the sap 
is seriously disturbed. The puparia occur in early spring in cells 
under a comparatively thin layer of bark, a portion of which is 
somewhat dried and with a distinctly lower vitality than normal 
bark. These conditions suggest applications of a miscible oil, since 
there is a chance that the cells will be penetrated and a considerable 
number of the insects destroyed. Unfortunately conditions pre- 
vented testing this method the past season. 
