REPORT OF THE SOCIETY 105 



LARVAL HABITS 



The larva on hatching usually enters the bark at a point just below the 

 egg; but there were instances where this did not occur. Instead, the larvae 

 remained congregated on the surface beneath the batch of empty shells, actively 

 laying down fine webs and exhibiting signs of unrest. This work went on 

 for a day or two and gradually ceased as the larvae burrowed into small cre- 

 vices near by. 



One of the most reliable signs of early larval operations is the presence of 

 small quantities of brown sand-hke casting held loosely together by invisible 

 threads of silk. These castings may be found chiefly in ths bark crevices and 

 about the creases of calbus formations. Another indication is a discoloured 

 spot on the bark, somewhat circular, from a quarter to one half inch in diameter, 

 with a darkened centre from which sap may be oozing. 



Thus established the young borer begins slowly to extend the very small 

 cavity, enlarging it shghtly as it proceeds inwards through the bark tissues. 

 The space cleared in this way by the end of the summer will be about an inch 

 or so in diameter, depending upon the character of the bark, that of younger 

 trees being softer and more succulent, and the boring itself not deeper than 

 three eighths to one-half of an inch. Here in this small gallery the larva spends 

 the first winter. Next spring, about the early part of May, it begins to extend 

 the site of the first year's operations and not only will bore deeper but also 

 widen its tunnel and chisel it irregularly back and forth in the inner bark and outer 

 layers of wood. Often two or three larvae will be working together in one of these 

 galleries and will clean away and skeletonize an irregular area of several inches 

 across with branch tunnels leading off in various directions. It is during 

 this stage of larval activity that much serious damage is done, large boughs 

 sometimes being girdled and trunks badly disfigured on their surfaces. 



As summer progress the larva continues inwards and attacks the outer 

 rings of the sapwood, passing on to the harder material of the heart-wood where 

 it hibernates. One larva dug from its winter quarters was curled in the shape 

 of the letter S, that is, the anterior segments of the body were bent over towards 

 the back, and the posterior ones turned inward over the venter. The creature 

 appeared lifeles.5 when removed, and for some time afterwards, efforts to arouse 

 it were without effect. On bringing it indoors, however, it revived and moved 

 about actively. Other srecimen.s taken from their winter cells in the outer woody 

 rings exhibited this curvature of the body, some showed this more than others, 

 for the most part at the abdominal end. 



The foUowirg spring, the beginning of the third year period of the larva, 

 the boring operatiors now having reached the heart-wood are carried further 

 inwards, often with a tendency upwards. After proceeding in this way for an 

 inch or so the larva in many cases will turn and tunnel straight upwards into 

 the very centre of the tree, returning from time to time to the mouth of the tun- 

 nel to remove excrement pellets and boring dust, and also to cut back the tunnel 

 walls in order to provide the necessary accommodation for its growing body. By 

 the end of the third summer the entire gallery will be about the same diameter 

 from end to end and excavated to a distance of twelve inches or even more 

 from the point of entry. In September the larva prepares for pupation. In this 

 state it spends its last winter; but if for any reason it should hibernate as a 

 larva, as sometimes happens, emergence will be delayed the next summer. 



Occasionally, an exit will become blocked in some unusual way. A pupa 

 endeavouring to reach the exterior will be unable to do so. This contingency 



