The Saw-Flies 



Many saw-flies are so injurious to vegetation as to possess 

 much economic importance; the larch saw-fly (Nematus erich- 

 sonii), in certain years, has destroyed large sections of larch 

 forests in northern New 



England through the work of its 



Fig. 44. — Cimbex americana. (After Riley.) 



larvae; the imported currant worm (Nematus ribesii) is a famous 

 enemy of currants in most parts of the United States; the com- 

 mon rose slug (Monostegia rosce), next to the so-called green 

 flies and the rose chafer, is the most abundant enemy to rose 



74 



