OF WASHINGTON, VOLUME XIII, 1911. 107 



NOTES ON A SAWFLY INJURIOUS TO ASH. 



(Hymenoptera; Tenthridinidae.) 



PLATE VII. 

 BY E. R. SASSCER. 



For several seasons the row of white ash, Frnxinns umeri- 

 , located near the coruer of Seventh and B streets N. W., 

 Washington, D. C., has suffered more or less injury through 

 the attacks of the larvae of a sawfly. In the spring of 1909 

 they were present in great numbers, and in fact the abun- 

 dance of the larvae on some trees was such that the leaves, es- 

 pecially those on the upper branches, were completely de- 

 voured. The adults of this sawfly were issuing April 18 in 

 quantities, and by the use of a collector's net they could be cap- 

 tured by the hundreds, fully 75 per cent of which were males. 

 On the 19th they were even more conspicuous, but owing to a 

 heavy precipitation on the two succeeding days no adults were 

 observed. On the 22d they could be seen flying about the 

 branches in limited numbers, and the issuing and oviposition 

 continued until the first week of May. 



In ovipositing the female sawfly, after careful deliberation, 

 with head pointed downward, thrusts her ovipositor Under 

 the epidermis near the margin of the leaf, after which she 

 usually flies to another leaf and repeats the operation. Al- 

 though a number of leaves were examined, in only a few in- 

 stances could more than one egg be found, and in every case 

 it was inserted in the edge and not in the petiole or midrib, 

 as is sometimes done by closely related species. 



The egg is oval, transparent, and at first rather difficult to 

 detect, but as the time for hatching approaches the dark color 

 of the head becomes visible. On May 4 they were hatching 

 in great numbers. The following is an illustration of the 

 development of the larva? for the brood of 1909: 



May 4. First larvae observed feeding on underside of leaves. 

 Newly hatched larvae are from 2 to 3 mm. in length, head 0.40 to 0.50 

 mm. in diameter, shiny and dark brown; body yellowish white with 

 transverse wrinkles; thoracic legs brownish, abdominal legs whitish; 

 thoracic segments a trifle larger than those on remainder of the body; 

 eyes black. 



May 5. First moult. Length of larvae 3 to 4 mm.; head 0.40 to 

 0.60 mm. in diameter. At this stage the larva is light greenish yel- 

 low, resembling in color somewhat the underside of the leaf; trans- 

 parent, with alimentary canal plainly visible through the skin. 



May 6. Second moult. Length of larva 4 to f> mm.; head 0.75 to 

 0.80 mm. in diameter, color much the same as in previous stage. 



May 7. Third moult. Length of larva 6 to 10 mm.; head 1 to 1.80 

 mm. in diameter. Body assuming a yellowish tinge with light lateral 



