NOVEMBER, 1861. 169 



LlTHOCOLLETIS. 

 Habits of the Larva. 



The larvas mine the leaves of trees, shrubs or low plants, 

 separating either the upper or lower cuticle and feeding on 

 the inner substance of the leaf. When the mine is on the 

 upper surface, or at least most frequently when it is in this 

 position, the leaf becomes folded and curved at the place 

 mined, and the separated cuticle is gathered into folds or 

 covers the curved portion so as to make a capacious habita- 

 tion. Some of the miners of the upper surface of leaves 

 make large blotches or tracts, and when the mines are fresh 

 the separated cuticle is whitish and very noticeable. The 

 miners of the under surface cause the upper cuticle to be 

 discoloured in patches, and this with the fold of the side of 

 the leaf is often sufficient to indicate the presence of a mine. 



Usually the species are confined to a single plant ; some, 

 however, feed on several allied plants. 



The larva never quits the mine and changes in it to a pupa. 

 Some species make no cocoon, others only a very slight one, 

 and others make one of grains of excrement woven together 

 with silk. 



Many of the species of the fall brood remain in the pupa 

 state during the winter, and appear as imagos in the spring, 

 and some of the imagos that appear late in the fall seem to 

 hybernate during the winter in the imago state. The spring 

 brood of larvas produce imagos in the summer. 



When the imagos escape from the mine the pupa case is 

 thrust through the separated cuticle, and left there after the 

 escape of the imago. 



1. L. salicifoliella. During the latter part of June or 

 early in July the leaves of yellow willow, Salix vitellina, var. 

 S. alba, should be searched for this insect. The mine is on 

 the under surface, usually near the base of the leaf and along 

 the edge. I found these mines for the first time on the 

 23rd of July of the present year, but they were untenanted, 



