686 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



ribs. Sometimes two rows of these blisters are found on the same leaf. The place 

 of insertion of the ovipositor is always plainly visible, as a nearly straight slit 

 {usually closed) of ferruginous or brownish color at or near that edge of the blister 

 which is nearest to the margin of the leaf, thus indicating that while ovipositing 

 the female fly grasps the edge of the leaf with her fore legs. (Fig. 194, a.) 



Leaves infested with eggs, although not rare, were by no means so abundant as 

 should have been expected from the extent of the injury inflicted by the imagos. A 

 great many plants (and among them many with their tops cut off) were not infested, 

 while occasionally a plant could be found with four or five infested leaves, mostly 

 about the middle or near the top of the plant. 



The egg, when about ready to hatch, is oblong oval, somewhat flattened, and with 

 its shell so thin and pliable that it not only loses its regular shape by the slightest 

 pressure, but even by the position or movements of the embryo larva within. The 

 shell is perfectly hyaline, with no visible sculpture besides some fine, irregular, and 

 variable wrinkles. Its surface is very sticky. At an earlier stage the egg is elon- 

 gate and nearly cylindrical. Through the whitish epidermis of the blister the shape 

 of the egg is always readily perceptible as a transverse (f. e., parallel or nearly 

 parallel to the margin of the leaf) object of a decided green color. (Fig. 194, c.) 



The young larva, after hatching remains for some time within the blister, but 

 finally leaves it through an irregular slit at the middle of the epidermis. Its color 

 is bluish gray. (Fig. 194, d.) 



The recently excluded larvae are uniformly curled up on the under side of the leaf. 



Three varieties of cultivated willows were found to be injured by the perfect saw- 

 fiy, while egg blisters could only be found on two varieties. 



The willows aifected were the American green ozier, the Welsh, and the Golden. 



Memedies. — It would be quite practicable, considering the small area to be pro- 

 tected and the conspicuous size of the insect and its clumsy movements, to catch the 

 perfect flies by means of a net ; but the application of arsenical poisons would be 

 surer, and would also rid the willows of many other enemies. 



*' For some years" says Mr. Bruner " the large saw-fly (Cimhex americana) has at- 

 tracted my attention at various points in Nebraska, bj' its habit of frequenting 

 hedges of white willow in preference to the various species of the native willow. 

 During the summer its large, green, slug-like larviB would be met with from time to 

 time, but not until the present summer have I learned that it appeared in such great 

 numbers as to completely defoliate the trees. 



"About three weeks ago (August 31) I visited Mr. G. M. Dodge, of Glencoe, Dodge 

 County, and while driving across the country observed that nearly every hedge of 

 this willow had been more or less injured by some insect which had stripped the 

 trees of most of their leaves. I at once attributed the work to the striped cotton- 

 wood beetle (Plagiodera scripta), which, as you have shown, has been known to injure 

 various species of willow, as well aa the poplars and cottonwood in this and other 

 sections of the country. Upon speaking to Mr. Dodge in reference to the subject, he 

 informed me that the work was that of the above named saw-fly. He also stated 

 that the larv£e had been so numerous on many of the hedges in his immediate neigh- 

 borhood as to completely defoliate the trees before they (the larvae) had attained full 

 growth, and that they had therefore proved the cause of their own destruction. 



"At otherpoints, however, where the larvae were less numerous, they have matured, 

 and will evidently make their appearance in force next season, provided no unfore- 

 seen providence intervenes. 



" Mr. Dodge also informed me that this saw-fly has been steadily on the increase for 

 the past three or four years — always working on the white willow in preference to 

 the native species." 



A Cimbex-like saw-fly larva occurred on the willow at Brunswick, Me., 

 August 6, 1886, September 3, 1885. It is represented by the very poor 

 sketch in PI. v, fig. 11. 



