ENEMIES. 19 



females have abortive wings, and a clue to the identity of the moth 

 is suggested. It is also quite possible that it is founded only on igno- 

 rance of the history of insects and the supposition that the moth and 

 caterpillar were of different sexes. 



Were it possible to identify this insect, enough might be known of 

 its habits to warrant predictions of its behavior in the future; under 

 the circumstances it is possible only to say that another attack may 

 occur at any time. Aside from the direct loss, the destruction of so 

 large a body of standing timber creates, as suggested by Dr. Hopkins, 

 a tire trap, which menaces the forests of the surrounding region, and 

 it is quite possible that many of the former large tires of the coast 

 region were due to this cause. With so great a rainfall and a dense 

 green underbrush, the forest seldom, if ever, becomes dry enough to 

 burn without some unusual aid, yet there is abundant evidence that 

 the whole region *has been swept clean by fire. It is difficult in any 

 other way to account for the existing stand of old red fir, since it is a 

 species which requires open ground for germination. 



BLACK CHECK. 



In 1900 the larvae of an insect were discovered living in the bark 

 and apparently causing a serious injury known as black check. 

 Investigation showed this process in all its stages — the fresh wound, 

 with the grub at work in it, partially covered scars of a year or two 

 ago, and blackened spots buried several inches where they would be 

 opened if the log came to the saw. The presence of larva is always 

 betrayed by a flow of resin. Several specimens were collected and 

 were identified b} r Messrs. Coquillot and Schwarz, of the Division 

 of Entomology, as an unknown species of the family of Syrphidse, 

 genus Xylota. Since it is the habit of this genus to ia} T its eggs in 

 the galleries of bark beetles, it seems probable that this species obtains 

 entrance in the same way, although no evidence was found to show 

 previous occupancy of the burrows. As such insects are often second- 

 ary and not originally responsible for the injury which is attributed to 

 them, careful search was made for similar burrows not occupied by 

 the Xylota larva, but none were found in an investigation carried on 

 for several months. The most plausible explanation is that the female 

 deposits the egg in the gallery of some Scolytid which does little or 

 no damage to the tree, and that the attack on the wood is made by the 

 Xylota larva upon emerging from the egg. In the fall the larva 

 leaves the cavity and buries itself in the mass of pitch which has col- 

 lected outside the bark, there assuming the pupal stage. 



The only forest region found wholly tree from this enemy was a 

 belt along the west slope of the Cascades, above an elevation of L,800 

 feet. If altitude proves responsible for this immunity, a similar 

 region in the Olympics will probably also he found free from attack. 



