156 NEW YORK STATE MUSEUM 



Ammen called his attention to the work of the adult tly. The tops in a 

 plantation of imported willows looked as if fire had run over it and on 

 investigation it was found that the mischief was due to their being gnawed 

 by the perfect fly, which made deep transverse incisions just below the dead 

 portion of the willow. The cut often extended more than half way around 

 the twig or else there were a number of smaller incisions one after the other. 



Professor Bruner writing of this species in 1888, states that this species 

 sometimes defoliates white willows growing as hedges in Nebraska, and 

 that it also infests the different native willows growing along the small 

 streams back from the timber belts bordering the larger water courses. He 

 adds that from upwards of 400 pupae collected he failed to rear a single 

 parasite. The cutting habit observed by Admiral Ammen was brought to 

 the attention of Prof. ¥. M. Webster in June 18S9 by a gentleman 

 residing in Nebraska. He states that thousands of the adult sawflies were 

 to be found flying among the tops of the largest trees, and adds that the 

 insects cut a rough gash with their jaws almost completely around the limb, 

 seeming to kill the outer bark as far as they go. Mr E. D. Ball observed 

 this same injury in Nebraska, and states that in his experience the slits 

 always heal over and that the principal injury is caused by the feeding of 

 the larvae. 



Life history. Dr Riley states that the eggs of this species are depos- 

 ited between the epidermis and parenchyma of the leaf and that when the 

 plant is examined from above, the place of oviposition is hardly perceptible, 

 it appearing as a very slight blisterlike swelling and accompanied on one 

 side by a faint ferruginous line. These blisters are very plainly seen on 

 the under surface of the leaf since they are much paler than the rest of the 

 surface, and in an advanced condition show a reddish tinge. He states 

 that they are always on the face of the leaf, usually nearer to the outer 

 margin than to the midrib, never on or near the midrib and rarely extend- 

 ing across one of the lateral veins. They may vary from one to nine or 

 more on a single leaf He states that the young larva after hatching 

 remains for some time within the blister and finally leaves it through an 



