112 



Insect Pests. 



run mainly up and down between the bark and wood. From these 

 median channels run, on either side, smaller ones, in which the larva? 

 live. There is a popular idea that only sickly or unhealthy trees are 

 attacked. That they are so more than others is very probable, but 

 perfectly sound trees suffer in the same way. 



The mere fact that we find larva- and pupce in the dying and dead 



wood does not neces- 

 sarily show that the 

 beetle only attacks 

 such wood. The larva? 

 have caused the un- 

 healthy state or have 

 killed the tree them- 

 selves, and have to 

 finish their develop- 

 ment where they have 

 lived. 



From various ob- 

 servations made, it- 

 appears that when once 

 a tree is invaded it 

 forms a centre that 

 attracts the beetles to 

 oviposit, and thus if we 

 only destroy it at the 

 right time, we can use 

 these damaged trees as 

 " trap trees " are used 

 in forestry. Both old 

 and young trees suffer. 

 In an old orchard 

 where trees have never 

 been tended, it is no 

 unusual thing to see 

 many of the smaller 



branches and twigs bared of bark and showing up pale against the 

 rest of the wood. This is usually due to this beetle. 



From these old neglected trees they invade young and sound ones. 



LIFE-HISTORY AND HABITS. 



The beetle that is the cause of this damage is quite small, often 

 no more than ^ inch. In colour it is nearly black, with some- 



[A. V. D. Rintoul. 



FIG. 93. PIECE OF PLUM STEM SHOWING "FLIGHT HOLES" 

 OF BARK BEETLF. (S. rugulosil*). 



(One-third natural size.) 



