340 The Large Poplar Longhom 



As the principal emergence period of the beetles in Scotland, is from 

 mid July to mid August, beetles should be looked for between these 

 dates and collected. 



To ascertain if the beetles have begun egg-laying, one has only to 

 examine very carefully the surface of that portion of the stems between 

 the level of the ground and nine inches upwards. As the reader will have 

 noticed in an earlier paragraph, if egg-laying has begun, egg-bites will 

 be found on these basal portions of the stems. These will have the 

 appearance of short, thin, narrow markings, measuring about 4-75 mm. 

 in length. To the left or right of each of these markings, lying either in 

 the bast layers if these be thick, or between the cambium layer and the 

 sapwood where the bast layers are thin, a single egg may be found. 



At a later date, i.e. in about one month's time these bites develop 

 into deep black cracks or scars, which, in course of time, become greatly 

 lengthened. 



As soon as larvae begin to groove the surface of the sapwood, their 

 presence is indicated by ^he protrusion of coarse shreds of gnawed wood, 

 which are thrust out through the egg-incisions. In the first year of 

 larval life, the presence of larvae in infested stems is not well marked. 

 It is while tunnelling the vertical portions of their galleries, that external 

 symptoms of larval attack become very apparent. The presence of the 

 larvae is then plainly indicated by large quantities of sawdust and wood 

 chips, lying in heaps at the bases of the stems, having been pushed out 

 by the larvae either through the exit hole or through cracks on the stem. 



Then there is the presence of the exit holes which occur from the 

 base to well up the stem. Should these holes be found on examination 

 to be packed tightly with frass and to be oval in section, then the adults 

 have not yet issued through them. On the other hand, if these holes be 

 circular in shape and empty, then adults have escaped from the stem. 

 In older stems which had survived earlier attacks, it was common to find 

 the flight holes greatly enlarged, and appearing as longitudinal fissures 

 on the surface of the stems (Plate XXIII). 



Control Measures. 



With a knowledge of the life history and habits of the species, it is 

 now possible to make definite recommendations and suggestions for 

 its control should it ever become necessary. 



Trees grown both in natural regeneration and in artificial plantations, 

 if already infested, should be cut down and burned, as they will be a 

 source of danger to healthier trees. This operation should be carried 



