Biological Papers. 159 



afflicted trees in autumn and winter before the beetles have 

 a chance to emerge from the trunks." 



There seems to be no indication or evidence whatever that 

 the above-mentioned borers had attacked perfectly healthy- 

 trees, but rather those which had begun to die from some 

 unknown cause. An examination of several trees which ex- 

 hibited the first signs of dying, denoted by a premature shed- 

 ding of the leaves, proved them to be entirely sound, and, with 

 one exception, failed to reveal the least trace of any insect at 

 work in them. This one exception pertained to an older tree 

 from which Tremex columha and a larva of Chrysobothris 

 femorata were removed, but the presence of these specimens 

 could only be regarded as an incidental matter having nothing 

 to do with the primary cause of the tree's failure in health. 

 In no instance could the responsibility for the original trou- 

 ble be charged to the elm-borer, Saperda tridentata, or its 

 companion, Magdalis armicollis, both of which> however, in- 

 fested diseased trees of long standing. That the first stages 

 in the dying of the trees, in whole or in part, as shown by 

 the wilting and falling of the leaves before the usual time, 

 were due to some disease, was consequently inferred. If such 

 trees are allowed to stand in this enfeebled condition, they 

 invite the attacks of borers as mentioned, and their complete 

 death would eventually result. Nevertheless, the claim is 

 made by eminent authorities that the elm Saperda will attack 

 healthy trees. 



The particulars concerning the different species of insects 

 secured from dead and dying elm during the progress of my 

 investigation as stated are herewith embodied, with a list of 

 determinations. 



ATTACKING THE TRUNK. 



Saperda tridentata Olivier. (The common elm-tree borer.) 

 Numerous larvae collected September 26, 1904 ; adults emerged 

 May 9 and 12, 1905, from section of tree kept in breeding 

 cage. 



Chrysobothris femorata LeConte. (Commonly known as 

 the flat-headed apple-tree borer.) One larva in its burrow 

 between bark and sapwood, at a distance of about one foot 

 above ground, October 6, 1904; one adult emerged May 23, 

 1905, from section of tree kept in breeding-cage. Although 

 elm has been mentioned in literature as a food-plant of this 

 species, the authority for such a record appeared to be un- 



