50 TREE PLANTER'S MANUAL. 



rough bark the cracks are selected and thence the beetle enters the bark. 

 To make a hole large and deep enough to hide, the beetle requires from 

 two to three hours. All such holes are perfectly round, and their different 

 sizes indicate the sizes of the beetles that made them. 



Species that live in solid wood lead a life different from that of those 

 living in the bark. In the former case the mother makes all ramifications 

 of a burrow, and then deposits many eggs together. In this case the larvae 

 eat nothing but the sap that enters their tunnels. In the latter case the 

 larvas themselves have to make the secondary burrows, each living singly 

 in one. Of course, the primary tunnel is made by the mother. Dead trees 

 can not furnish food for either of these larvae, as they are without fluid 

 sap. If a tree should become too dry before the larvse mature all have to 

 perish for lack of food; if it should simply become very dry the length of 

 the larval existence will be greatly lengthened so as to give them time to 

 find all the food required to reach their full size. 



Most species of bark-beetles require about eight weeks to undergo all 

 their transformations from the egg to the adult insect, and consequently a 

 number of generations can be produced in a single year under favorable 

 conditions. It is of great practical importance to know the number of 

 generations, and the exact time in which the beetles swarm, since upon 

 this knowledge must rest the methods to combat them successfully. This 

 important knowledge is still lacking in the great majority of cases, and 

 before it is acquired all proposed remedies will be more or less unsuccessful. 

 Bad weather, rain and snow, except during the time of swarming, have but 

 little influence upon these noxious beetles, as they are so well hidden and 

 protected inside their solid home in a tree throughout almost their entire 

 period of existence. This explains why insects of this kind can exist in 

 such large numbers as far north as trees grow, and in the mountains 

 almost to the snow line. 



No other family of beetles is so destructive to trees as the one composed 

 of bark-beetles, and consequently they are feared whenever forests are 

 taken care of or where new ones are planted. 



As far as remedies are concerned, only a few practical ones can be men- 

 tioned. Since "an ounce of prevention is better than a pound of cure," we 

 have to remove all wood from the forests that has been cut a short time 

 before the swarming period of such beetles. This is very important. A 

 second remedy, and one that has to be carried out at the same time as the 

 first one, is to prepare some trees as traps for the insects flying about to 

 deposit their eggs. This will prevent them from depositing their eggs upon 

 more valuable trees. Removal of freshly cut trees from the forests without 

 preparing traps is worse than useless, as it is rather an invitation for the 

 insects to increase upon good timber trees. Since we know that bark- 

 beetles prefer recently injured trees, we have to prepare a number of such 

 trees as traps. In the bark of such trap-trees the majority of the flying 

 females will depo^*"- their eggs. By removing the bark of such trap-trees 

 after five or six treeks, and by burning the bark, an immense number of 

 the immature bark-beetles will be destroyed. By preparing a number of 



