REPORT OF THE STATE ENTOMOLOGIST I917 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 i\pril 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 destroj^ed. Unfortunately conditions pre- 

 vented testing this method the past season. 



