74 



Bulletin 234 



strongly marjsed in the order given. It seems from this that the beetles upon 

 leaving the birch feed on other trees iintil ihe time for reproducti<m. " 



The Life and Habits of the Insect 



The chain of evidence regarding the life-stpry of this bronze birch borer 

 is not yet quite complete, but from the records and from my observations and 

 investiga,tions most of the details can be supplied. 



Hiiernation. — All the evidence Ihave, shows that the insect always passes 

 the winter as a full-grown grub or borer curled up in a long, narrow cell or 

 chamber, which it makes in the wood not, far from the bark. I have failed to 

 find smaller borers in uncompleted burrows in autumn. One of these hiber- 

 nating cells is shown at c in Fig. 36. , Most of the borers may be found in these 

 cells early in October ; Adams reports finding some as early as July 14th. 

 Some of them can be easily located by cutting into the tree beneath the char- 

 acteristic rusty colored spots (Fig. 30, a). The grubs rest in the cells in a 

 peculiar manner with the cephalic third of the body bent around l)dng close to 

 the remainder. They are very sluggish when removed from the cells. Early 

 in the spring these hibernated borers shorten up, straighten out in their cells, 

 and thus prepare for transforming. ^ 



Transformation and habits in spring. — During the latter part of AprU or 

 early in May, depending upon weather conditions, the grubs transform in their 

 hibernating cells into the adult insects or beetles (Figs. 31 and 35). A day or 

 two before transforming the pupae turn to the dark bronzy color of the beetle. 



In making its hibernating and transforming chamber in the wood in early 

 autumn, the borer also extends its burrow up to the bark, so that- in the spring 

 the newly-transformed beetles only have to squeeze their way out of the ctU 

 and eat their way through the bark. Larsen records that the emergence of 

 the beetles is rather a laborious process, as some were found "with the for- 

 ward parts of their bodies protruding for hours making long rests between 

 €fforts to free themselves." 

 beetles are shown in Fig. 37. 

 Eleven exit holes have been 

 counted in an area only two 

 and a half inches in diameter. 



The date of emergence 

 •of the beetles in the spring is 

 of much importance in con- 

 nection with methods for 

 controlling it, and it varies 

 somewhat witli climatic and 

 other conditions. Sometimes 

 a few of them emerge as early 

 as May 1st, but my observa- 

 tions and breeding notes, in 

 New York, indicate that most 

 of them do not appear until 



Several of the peculiar shaped exit holes of the 



Fig. T,y.—2ix,t holes 0/ the bronze birch borer betiles in 



