SHADE TREE INSECTS 73 



The tiny grubs of this insect mine in the tissues between the upper and lower 

 epidermis of the leaves, especially of Caniperdovvn, English, and Scotch elms. 

 The mines appear first as tiny whitish spots but soon become large, blotchy, 

 whitish areas, bounded by the lateral leaf veins. Several grubs may attack a 

 single leaf, and their individual mines coalesce, hollowing out the whole leaf. 

 In this case the leaf will soon wither and fall. If only a small portion of the leaf is 

 mined the epidermis will dry and crack, leaving holes in the leaf. This injury 

 spoils the appearance of ornamental trees, and when the infestation is severe 

 seriously weakens them. 



Dcscriptioii. The adult is a tiny, shiny black sawfly. It is about 1/8 inch 

 long and has a wingspread of about 3-i inch. 



The mature grub is about 1/3 inch long, flat, and whitish in color with a pale 

 brown head. The legs are encircled with brown. 



The cocoons are very small, tough, brown, and c\ lindrical. 



Life History. The mature grubs hibernate in cocoons under the surface of the 

 soil. They pupate in the spring, and about the middle of Alay emerge as four- 

 winged flies. The females usually lay their eggs in the upper surface of the 

 lea\ es. During the latter half of May the young grubs begin to mine the leaves. 

 B>' earh' July they finish feeding, desert the mines, and go to the ground to con- 

 struct their cocoons. There is one generation a year. 



Control. This insect may be controlled by thoroughly spraying the foliage in 

 the spring, as soon as the tin\', blister-like mines appear, with 1 pint of 40 percent 

 nicotine sulfate to 100 gallons of water with 5 pounds of soap as a spreader. 



Felt, E. P. N. Y. State. Mus. Mem. 8(1) -.162-163. 1905. 



Herrick, G. W. Cornell Univ. Agr Exp. Sta. Bui. 333:508-511. 1913. 



Slingerland, M. V. Cornell Univ. .A.gr. Exp. Sta. Bui. 233:49-57. 1905. 



Elm Sav.'fly 



Cimhex americann Leach 



This large native insect is widely distributed in northern United States and 

 southern Canada. It attacks elm and willow chiefly but is also found on poplar, 

 ma[)le, linden, and alder. In Masbachusetts it is not considered to be important 

 although, because of its large size and the conspicuous color of the larvae, it occa- 

 siorially attracts attention. The laivae feed on the foliage and cause ni(jst of the 

 damage. The adult sawflies ha\e been reported occasionally to girdle the stems 

 ol willow. 



Elm Sawfly 



1. Larva on leaf Courtesy, Robert L. Coffin. 



2. Adult sawfly. 



