THE COMMON ELM-BORER. 225 
More recently the ravages of this borer have been observed by Pro- 
fessor Forbes, whose notes we copy from his third report on the injuri- 
ous insects of Illinois. 
For several years past my attention has been attracted by the gradual decay and 
death of the rows of white elms ( Ulmus americana) in the towns of Normal, Bloom- 
ington, and Champaign. The difficulty with the trees commonly commences to de- 
clare itself from the middle of summer to autumn, when the leaves, tirst 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. naturally followed speedily 
by the death of the branches themselves, as is clearly evident the following spriDg, 
when these remain black and lifeless while the rest of the tree is putting on its fol- 
iage. 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 diffi- 
culty, 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 autumn of 1883, 1 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 larvae of Saperda tridentata appeared in consider- 
able numbers in the still living parts of the wood, and those of Afagdalis armicollis 
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 August 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 re- 
moved, and a glass jar was inverted over the opening. 
Nothing emerged until the following spring, except a single parasite taken Septem- 
ber 14. On the 9th of April, living larvae of Saperda were found still within the 
wood, but no images had appeared in the boxes, neither were any pupae discovered. 
On the 17th of that mouth, both larvae and pupae were detected, and on the 2d of 
May the first imagos appeared, three in number. On the 3d another imago emerged, 
on the 5th five more, and on the 7th eighteen, on the 8th eleven, and on the 12th 
twenty-three, this being the largest number taken from the boxes at once. Beetles 
continued, however, to emerge at frequent intervals until the 22d of June, at which 
time the last appeared, one hundred and eighteen in all having been taken alive. 
On the 15th of September the boxes were opened finally, thoroughly searched, and 
fifty-three more dead Saperdas were found. The boxes in which these specimens 
transformed had been kept under cover, but at the natural temperature of the air. 
Although the elm borer has evidently been for several years both numerous and in- 
creasing in the neighborhood where this tree was destroyed, the amount of parasitism 
developed by the experiments was quite insignificant, only eight parasitic insects, 
belonging to three species, appearing in the boxes as against the one hundred and 
seventy-one examples of the adult borer ; and indeed, as the same pieces of wood con- 
tained a great host of the larvae of Afagdalis armicollis, from which multitudes of 
imagos of this species emerged during this spring, it is impossible to say that some or 
most of this small number of parasites may not have escaped from the latter species. 
From the present appearance of the elms throughout the towns of Central Illinois 
where I have had an opportunity to examine their condition, and from the rapid 
progress which this pest has made among them during the last two or three years, it 
extremely likely that it will totally exterminate the trees unless it be promptly 
5 ENT 15 
