254 



PROTECTION AGAINST INSECTS. 



The larvae appear in June and July ; the second brood in 

 August and September. 



Pupation : in July and August, in the bast or sap wood ; the 

 second brood, which hibernate as larvae, 

 pupate in the following May. 



Flight-period : in August. The second 

 brood is mature by June of the following 

 year, and is followed by a third brood in 

 the autumn which winter in the beetle 

 stage. 



The generation thus extends over 

 1J years. The beetle frequently appears 

 in company with T. lands, Fabr., and 

 is widely distributed. It is common in 

 conifer forests in Britain. 



c. Relations to the Forest. 

 The common Scots pine is the chief 

 tree attacked by this bark-beetle. It 

 has, however, been also found in the 

 Weymouth, cluster and mountain pines, 

 and E. Hartig has noticed it on the 

 spruce. It prefers the plants of 6 to 

 12 -year -old cultivations, and only 

 attacks the branches and twigs of older 

 trees, where the bark is thin. As, how- 

 ever, it attacks branches which are 

 thoroughly sound, the crowns of trees 

 are considerably thinned out by this 

 beetle, especially when other bark- 

 beetles and longicorn beetles join in 

 the attack. 



The bast and sapwood are both 

 attacked. The irregularly stellate 

 mother - galleries are generally 4 to 

 7-armed, rarely 3-armed. The branches of these galleries 

 run longitudinally rather than horizontally, and' have a 

 knotted appearance, as the egg chambers are large and 

 comparatively far apart. The larval galleries are somewhat 



Fig. 114. Burrows of T. 

 bidcntatus, Ilbst., on 

 pine sapwood. (Natural 

 size.) 

 a Pairing-chambers. 



