10 THE BLACK HILLS BEETLE. 



(2) The principal areas of recent damage by this beetle in the 

 reserve and on private lands are in the vicinity of Cascade and 

 Palmer Lake ; but evidence of old and new work was observed to be 

 more or less frequent in all sections visited. 



. (3) The evidence found on old, dead, standing, and felled trees of 

 the work of the Black Hills beetle on pine, the spruce-destroying 

 beetle {Dendroctonus piceaperda Hopk.) on Engelmann spruce, and 

 the Douglas spruce Dendroctonus (D. pseudotsugse Hopk. MSS.) on 

 Douglas spruce indicate that all of these species have been present and 

 destructive to living timber in this region for at least fifty years. 

 The number and distribution of such old beetle-marked trees indi- 

 cate that very extensive depredations have been wrought by them 

 in the Pikes Peak region within the past century; and present 

 conditions also indicate that a large per cent of the vast destruction 

 of timber, heretofore attributed to fire, was primarily due to the 

 work of these insects. 



(4) The three species of bark beetles above mentioned are without 

 doubt the most important insect enemies of conifer forests in the 

 central Rocky Mountain region; hence they are a constant menace 

 to the remaining living timber in and around the reserves of central 

 Colorado. 



While at present the spruce-destroying beetle appears to be rare, 



and the Douglas spruce and Black Hills beetles are not common 



enough to cause extensive depredations, it is plain, from what is 



known of the destructive powers of these insects, that if neglected 



and if specially favorable conditions for their multiplication should 



prevail for two or more years in succession they could easily destroy 



all of the timber of commercial size and a large per cent of the< 



reproduction. 



THE BLACK HILLS BEETLE. 



The Black Hills beetle (D. ponderosse) is at present the most com- 

 mon and destructive enemy of the living pine timber in and around 

 the Pikes Peak Reserve; therefore it should receive primary con- 

 sideration. 



The best success in any efforts by forest officials or private owners 

 of forests to control this beetle will depend on a sufficient knowledge 

 of the species, its habits, life history, and the influences which are 

 favorable or unfavorable for its increase and destructive invasions. 



Insufficient knowledge on these points results in the confusion of 

 the primary and secondary enemies of the tree, unnecessary expendi- 

 ture of time and money, by felling and barking trees at the wrong 

 time of the year, or after the broods of the primary enemy have 

 emerged, the felling of living trees which would have recovered, 

 and the unnecessary destruction of beneficial insects and insect dis- 

 eases by burning the bark. 



