CHAP, xiv.] Insect Enemies 325 



Such decoy-stems should be felled and laid in position early 

 in the season, before the insects are likely to swarm, as many 

 species naturally seek after diseased and recently felled trees 

 before attempting to deposit their ova in healthy stems, whose 

 strong resinous exudation to a considerable extent threatens the 

 well-being of their brood. Stems that have thus been placed as 

 decoys in winter or early spring must be barked and removed 

 during May and June ; and fresh decoy-stems must be made to 

 take their place in summer, so as to catch the second brood of 

 species having a double generation. For such decoys, domi- 

 nated or suppressed, but still healthy, poles or trees should be 

 selected, and not half-dry stems that are already nearly dead ; 

 otherwise these present no great attractions to the females in 

 search of breeding-places. It is also well to support them upon 

 rests so as to raise them off the ground and let the beetles and 

 weevils have full access to the lower side, which remains fresh 

 and sappy after the upper half is becoming dry. The branches 

 (which may also be used for decoy purposes for many species) 

 should be lopped off the stems in order to obviate the evapora- 

 tion which would otherwise be continued through the foliage. 

 Timber from the winter fall may thus be used for decoy pur- 

 poses ; but it must be removed and carefully barked not later 

 than the middle of May. Its removal alone is not sufficient ; 

 for then the broods develop normally, and increase prolifically. 



The decoy-stems should be examined from time to time 

 to see if they have been successful in luring insects to deposit 

 their ova there. This may be noted by small drops of resin or 

 heaps of bore-dust near the punctures and bore-holes; but pieces 

 of the bark should also be removed occasionally to see how 

 far the young brood has developed. When the largest larvae 

 appear about half-grown the proper time has come for the bark 

 to be stripped and burned, as until then there would always 

 be the danger of beetles, whose ovi-deposition was not yet 

 completed, being able to continue their reproduction elsewhere. 



Attempts to collect the larvae can only be made in the case 



