112 



AKTICLE VII. INSECTS INJURIOUS TO THE ELM. 



1. The Elm Borer, (Saperda trldentata, Oliv.) 



Order Coleoptera. Family Cerambycid.e. 



(Plate XII. Fig 2.) 



For several years past my attention has been attracted by the 

 gradual decay and death of the rows of white elms {Vlrmis americana) 

 in the towns of Normal, Bloomington, and Champaign. The difficulty 

 with the trees commonly commences, to declare itself from the mid- 

 dle of summer to autumn, when the leaves, first upon the terminal 

 twigs and then upon the larger branches, are seen to stop their 

 growth, change their color, and ultimately to fall. This loss is nat- 

 urally followed speedily by the death of the branches themselves, 

 as is clearly evident the following spring, when these remain black 

 and lifeless while the rest of the tree is putting on its foliage. 

 Usually the higher branches of the tree are those first affected, but 

 the whole top soon seems to blight, and in a year or two the tree 

 perishes utterly. This difficulty, commencing here and there, extends 

 slowly from tree to tree along the rows, finally inevitably destroying 

 every tree of this species in the immediate vicinity. 



In the autumn of 1883, I directed an assistant, Mr. Webster, to 

 dig up a tree which had nearly died in this manner during the 

 summer, and to carefully examine the larger rOots, the trunk, and 

 all the branches, with a view to ascertaining, if practicable, the 

 cause of the difficulty. The roots were found unaffected, but on 

 peeling the bark from the trunk, about half-grown larvfe of Sa'pcrda 

 tridentata appeared in considerable numbers in the still living parts 

 of the wood, and those of Magdalis arrnicolUs (Plate Xlf Fig. 3) 

 were abundant where the bark and wood were already dead. The 

 manner in which the bark had been mined and burrowed by the 

 Saperdas, gave sufficient evidence of the cause of the death of the 

 tree, the borers having again and again completely girdled the trunk. 



Both the trunk and branches of this tree were cut up in lengths 

 and boxed for the purpose of determining the details of the life 

 history of the species. The specimens were boxed Aug. 8, the 

 cracks of the boxes being closed by pasting over them strips of 

 paper, and each having left a glass covered opening in the top, to 

 which it was assumed that the insects emerging would be attracted. 

 Later, this cover was removed, and a glass jar was inverted over 

 the opening. 



