224 LEAF-MINING INSECTS 



successful in the case of hawthorn but to have very little 

 influence in the case of cherry. This difference is doubtless 

 due to differences in the cuticle of the leaves. Hydrocyanic 

 acid fumigation was effective but is not practicable for 

 ordinary cherry plantings. The one remedy recommended 

 is that of picking the infected foliage early in the season. 



Fenusa varipes. In the type genus of this subfamily there 

 are an imported European and probably a native species. 

 Fenusa varipes mines the leaves of native alders particularly 

 Alnus incana in August and September. Dyar reports this 

 species for the eastern states and Webster for Ottawa Canada 

 and vicinity. In the fall of 1916 it was very common in the 

 alders at Fredericton, New Brunswick. In late September 

 and early October many larvae were still in the leaves. 

 The larvae were found in the newer leaves at the ends of 

 the twigs and on new shoots. These mines were nearly 

 completed and the larvae left the leaves in a few days. 

 There were also very many empty mines some of which 

 seemed to have been recently vacated and others of which 

 seemed to have been made much earlier in the season and 

 so long deserted that the cuticles were dried and cracked 

 and worn away. If all these mines were of one species 

 then the species must be either double brooded or different 

 individuals must vary greatly in the time of mining and 

 emerging. 



Mined leaves were brought into the laboratory and placed 

 in tin boxes with damp earth. By the middle of October 

 all the mines were empty and the larvae were buried in the 

 soil. The completed mines were about 6 mm. w T ide and 30 

 mm. long, being confined for the most part between succes- 

 sive lateral veins. They were less transparent than other 

 sawfly mines on such host plants as elm, rubus sp., violet 

 or hawthorn. Both sides of the mines become dark brown 

 and rather dry. The frass is abundant and scattered 

 through the mine. 



