294 WEST VIRGINIA EXPERIMENT STATION 



general appearance indicated that they had been attacked by the charact- 

 eristic trouble which was shown in a few yellow leaves at the tops. The 

 roots of such trees were found in a perfectly healthy condition for some 

 distance beneath the surface; the bark on the trunks from a 

 distanc of from five to fifteen feet from the base was green, 

 full of sap, and apparently healthy; the leaves were almost free 

 from insect attack or disease, in no case was there sufficient attack of 

 this nature to indicate even a slight injury; the bark, however, at a point 

 about two-thirds up from the base of the tree, was found in every case to 

 be infested by Dendroctonus frontalis in sufficient numbers to kill all the bark 

 for some distance above that point, and in this bark fully developed bee- 

 tles and pupae were fonnd on May 5th, thus indicating that the eggs 

 must have been deposited in the bark the previous summer or fall. All 

 of the characteristic dead and dying pine and spruce trees examined 

 showed abundant evidence that they had been invaded while yet living 

 by this bark beetle. 



It would seem that the turpentine escaping into the burrows made by 

 the beetles in the living bark would render the conditions unfavorable for 

 the progress of their work. They have, however, the power of removing 

 it from their burrows, and they manipulate the sticky resinous substance 

 with seemingly as much ease and in a like manner as the crawfish does 

 the clay it piles up around its burrow. Often a half teaspoonful of the 

 pitch will be found massed about the entrance to the burrows made by 

 the beetle. The} 7 push the turpentine out through a hole kept open in the 

 pitchy, adhesive mass. I have observed them backing out from the en- 

 trance, shoving behind them a quantity of turpentine, and at the same 

 time they would be completely enveloped by it. 



Trees invaded by these beetles the previous fall may remain green until 

 spring when they are usually attacked by the large Dendroctonus terebrans, 

 Hylurgops glabratus and Tomicus calligraphus, the-two former at the base of 

 the tree, the latter in the green bark above. They are in turn followed 

 by numerous species of bark and timber beetles nntil the invaded trees 

 may be, as I have found, the hosts of at least twenty-five species of scoly- 

 tids coming like reinforcements to the aid of D frontalis to make doubly 

 sure of the death of the invaded trees. Later on, these Scolytids are fol- 

 lowed by insects belonging to other families until a dead or dying tree 

 may be the host of hundreds of species and millions of examples, breeding 

 in and feeding upon every part of the tree from the base to the terminal 

 twigs, rendering it worthless for lumber within a year after it dies. 



It will be seen that Dendroctonus frontalis may be the primary cause of 

 not only the death of the trees but of their rapid decay. 



West Va. Agricultural Experiment Station, Morgantown, West Va. , 

 July 20, 1892. 



THE CONSIDERATION OF REMEDIES. 



As stated in a subsequent article to Insect Life, a copy 01 

 which will be found further on in this report, the possibility of 

 applying a remedy against the rapidly spreading ravages of the 

 destructive bark beetle seemed out of the question, but when 

 it was found in June, 1892, that the insects had just commenced 

 their attack upon the extensive forests of black spruce and 

 white pine, it indicated that possibly some method could be 



