II. A EUROPEAN ALDER SAWFLY LEAF-MINER 



Kaliosysphinga dohrnii Tischbein 



The European alder {Alnus glutinosd) and its cut-leaved varieties are 

 often planted as ornamental trees in America where they have become 

 naturalized in some localities. In Europe the leaves of this alder are preyed 

 upon by several insects, and at least one of these enemies has been injuring 

 these trees in America for several years. 



In June, 1891, a nurseryman at Newark, N. Y. sent me several leaves of 

 European alder with large brown patches or "blisters " on the upper side, as 

 shown in Fig. 29. I soon found that a large tree on the Cornell University 



Fig. 29. — Work of the European alder sawfly leaf-miner, 

 the brown blisters or mines. Nearly natural size. 



Several larva lived in 



Campus, and one tree of the cut-leaved variety near the Campus also bore 

 many of these " blistered " leaves. There were several small larvae living in 

 each large " blister " which they had caused by mining in the leaf just under 

 the upper epidermis. The half dozen European alders planted on the Campus 

 in later years were soon infested by the insects, and during the past season 

 many of the leaves on these trees were so badly " blistered " that the ground 

 beneath was strewn with the brown, dead leaves, and the trees presented a 

 very ragged appearance from July till autumn. Thus the insect is capable of 

 seriously injuring these desirable ornamental trees. A study of the life and 

 habits of this alder pest was begun in 1 89 1 , but was interrupted for several 

 years, and finally completed during the past year. 



The insect. — Within the brown mines or " blisters " on the leaves may 

 be found in summer from one to a dozen or more slender, whitish larvse or 



