THE GENUS DENDEOCTONUS. 



145 



all of them about 35 years old. Gliick in 1876 cites a very strong attack in Rheinfalz 

 near Coblenz. Since then the insect appeared everywhere and complaints arise 

 every year in German forest literature. We know that the insect in its continual 

 extension toward the west, after having seriously ravaged the plantings of Eiffel 

 and of German Herzogenwald, has finished by reaching our frontier, and that it was 

 discovered for the first time in Belgium in 1896 in Herzogenwald. 



It is quite clear that the preparation of trap trees in the sense that one understands 

 them for the other scolytids can accomplish nothing. 



The remedial measures in actual use are as follows: When the laborer going to his 

 work in Herzogenwald, or the forest officer on his circuit, notices any of the character- 

 istic signs of the attack of D. micans he does not fail to make known at once his dis- 

 covery. In order to easily find the tree again he should attach around the trunk a 

 belt of ferns or grass. At certain periods, several times during the dangerous months, 

 later not so often, a worker, armed with a knife and a pruning knife, sometimes with 

 a light ladder and a pail of coal tar or tar, makes the inspection of the contaminated 

 region. 



Fig. 94.— The European spruce beetle: Distribution map. (Author's illustration.) 



After having encircled the tree with a special apron of twist, he raises the bark at 

 the place of attack, cleans out the wound made by the larvae, and re-covers it with 

 the liquid preservative. The dried particles taken out are given to the fire and 

 destroyed to the last particle, except during the months of summer, when the parasite, 

 Pimpla terebrans, is to be found. When these are found it is necessary to examine 

 the debris upon a sheet or cloth. 



In order to clean out the wounds found upon the roots at their branching, a tool in 

 the form of a recurved spade is used. 



The expense resulting from such surveillance and the work of cleaning is net excess- 

 ive when the attack is in its infancy and the trees attacked are not yet numerous. 



Rarely it happens that the tree must be cut down. 



It is not the same when the insect has been able to install itself in a planting for 

 several years and to form serious breeding places. In order to avoid, then, making 

 clearings in the middle of dense plantings, it is necessary to proceed with great pru- 

 dence, to clear out with circumspection, and to sometimes clean the trees high and 

 low when this is still possible. It is estimated that trees which are not attacked for 

 more than two-thirds of the circumference of the trunk can in this extreme case be 

 cleaned out and re-covered carefully with coal tar or tar. 

 89535— Bull. 83, pt. 1—09 11 



