THE PINE INVESTIGATION. 389 



ence of Scolytids. Since the trees killed by fire may offer fa- 

 vorable conditions for their multiplication, while vast numbers 

 are destroyed by forest fires; so that as lar as forest flres are 

 concerned, the favorable and unfavorable conditions are about 

 equally balanced. 



BIRDS AS FRIENDS OF SCOLYTIDS. 



Birds may be friendly in their relations to Scolytids both in 

 destroying their predaceous and parasitic enemies, and, as in 

 the case of the yellow-bellied woodpecker, may be so injurious 

 to trees as to offer favorable conditions for the attack of 

 bark and timber beetles. The punctures in the bark made by 

 the birds are also often utilized by bark and timber beetles for 

 -their entrance into the bark and wood; thus they are saved 

 the labor of boring through the hard outer bark. Birds are 

 especially useful to Scolytids in feeding upon their worst ene- 

 mies the Clerids, since both the adults and larvae of the 

 Clerids are doubtless destroyed in great numbers by wood- 

 peckers and other insectiverous birds. (See enemies of Olerids 

 on another page.) 



CLIMATIC AND OTHER NATURAL CONDITIONS FAVORABLE TO THE EX- 

 ISTENCE OF SCOLYTIDS. 



Besides the favorable conditions for the existence and multi- 

 plication of Scolytids through the influence of man, there are 

 many natural conditions which contribute to their welfare: trees 

 broken or felled by storms or broken by snow offer most excel- 

 lent conditions for the attack and multiplication of numerous 

 species of Scolytids, as does the small and large shrubs and 

 trees, and the twigs and branches, which are weakened or 

 killed by natural causes. A warm, rainy season is also sup- 

 posed to be especially favorable for the breeding habits of cer- 

 tain Scolytids, since a certain amount of moisture in the bark 

 and wood infested by them, is necessary for their rapid de- 

 velopment. 



PREVENTIVES AND REMEDIES- 

 PREVENTIVES. 



The best preventives against attack of injurious and even 



