18 



Dendroctonus, Tomicus, and other Scolytids attacking the defoliated 

 and partly defoliated trees. ]Vfy observations led me to conclude that 

 were it not for the secondary attack of the Scolytids many of these 

 trees would have recovered from the injuries by the butterfly larvae. 

 Indeed, it seems to me that this association of bark beetles with defo- 

 liating caterpillars in causing the death of trees is an important feature 

 to be taken into consideration in any study of troubles of this character. 



The work of the supposed geometrid larva, found near Ahlers, 

 Oreg., has not, I believe, been previously recorded, and, while I did 

 not have an opportunity to see specimens of this insect, which has not 

 attracted attention since the summer and fall of 1890, 1 obtained some 

 valuable information from Mr. Ahlers regarding the character of the 

 invasion, the insect, and the extent of its depredations. 



Mr. Ahlers, postmaster at Ahlers, took a course in entomology at 

 Wernigerode am Harz, Province of Saxony. Hence, his observations 

 are of especial interest. Mr. Ahlers said: 



The worms commenced to attract a little attention here in 1889. A few moths 

 were seen in the fall of the same year. In July, 1890, the worms appeared in great 

 numbers, the first on the hemlock, feeding on the base of the leaves and cutting 

 them off. When standing beneath the trees the droppings from the insects and the 

 falling leaves sounded like rain. "When all of the leaves were eaten from the trees 

 the worms would let themselves down by means of webs, and, if they were not full 

 grown, would feed on the leaves of all kinds of shrubs and trees, except the Douglas 

 spruce and cedar. The worms were observed during July and August, and disap- 

 peared in the latter month, probably going into the ground to pupate. In October 

 the moths began to come out. They were grayish white with dark markings on the 

 wings. The wings spread about 1J inches. The moths Avould appear on the wing 

 about 3 o'clock in the afternoon in enormous swarms around the tops of the trees, 

 resembling a white cloud. They continued to fly for about three weeks, at the end 

 of which time the ground was covered with the dead insects, and the small streams 

 were filled with them, in some places forming dams. The next year, 1891, they 

 attacked the Sitka spruce and defoliated the trees, which died the following fall or 

 winter. * * * When the worms were coming down from the trees the webs 

 made the trees look as if they were covered with a grayish veil. The worms were 

 about 1J inches long, the sides grayish green, with darker gray zigzag markings 

 on the back. When traveling they measured their way. This trouble extended 

 over parts of Clatsop and Tillamook counties, killing all the hemlock and Sitka 

 spruce in a belt between an elevation of about 450 and 1,200 feet above tide. The 

 Douglas spruce and red cedar were not injured. 



At the time of my visit much of the area covered by dead timber 

 had been frequently burned over by forest fires, so that in some places 

 nearly all of the dead timber had disappeared, but in other places, 

 where the conditions had not been so favorable for the spread of the 

 fire, the dead, barkless trunks of the trees were still standing, the tops 

 broken and the branches fallen, the scene presenting at once a most 

 impressive example of the destructive powers of an insect enemy of 

 forests and of subsequent devastation by forest fires. 



When it is considered that some of the spruce which grow here are 

 10 to 13 feet in diameter, 300 feet tall, and will yield more lumber 



