THE WESTERN PINE-DESTROYING BAEKBEETLE. 21 



to attack and kill the timber in adjoining healthy forests. Indeed, my observation leads me 

 to conclude that a considerable number of girdled pine trees may easily form a nucleus for a 

 destructive invasion by it. 



In the same bulletin, under the head of " The western yellow pine," 

 he says : 



It has in Dendroctonus brevicomis a most pernicious enemy, which penetrates and exca- 

 vates winding galleries through the Jiving bark of the finest trees, thus speedily causing t heir 

 death. Very many trees have died and are dying from this cause, and the dead ones are 

 contributing to the spread of forest fires. 



Specimens of the insect and its work occupied a prominent place in 

 the exhaustive exhibit of insect enemies of forests and forest products 

 at the Louisiana Purchase Exposition at St. Louis, in 1904, and the 

 Lewis and Clark Centennial Exposition at Portland, Oregon, in 1905, 

 and were referred to in the catalogues of the exhibits by the Bureau 

 of Entomology. a 



OBSERVATIONS BY HOPKINS, 1899-1904. 



The following summary relating to this species, prepared by Doctor 

 Hopkins from his field notes, includes many facts which have not been 

 published and which have a direct bearing on the life history and 

 habits of the species in different sections of the country where it is 

 found : 



McCloud, Cal., April 21, 1899. — Work and dead adults were dis- 

 covered in a sugar pine log, evidently from a tree which was dying 

 when felled ; also dead parent adults in primary galleries, and larvae and 

 pupae abundant in outer bark of large dying western } T ellow pine with 

 the characteristic appearance of eastern pines when dying from the 

 attack of the destructive pine barkbeetle, D. frontalis. A few imma- 

 ture adults were found in the outer bark, and evidence that some had 

 emerged. This evidence was in the form of apparent exit holes in the 

 bark, which may have been ventilating holes from main galleries, for 

 with our present knowledge it is not likely that any adults could have 

 emerged so early. 



Grants Pass, Oregon, 1899. — On April 24 numerous dying western 

 yellow pine trees were found here scattered through the forest where 

 a severe windstorm had blown down much large timber on Septem- 

 ber 24, 1895. Young adults, larvae, and pupae were found in the outer 

 bark of the standing trees which had evidently been attacked and had 

 commenced to die the previous fall. April 25, numerous trees were 

 observed which died the fall before and others which were not vet 

 dead. One group of 30 young trees about 2 miles north of town were 

 dying at the top, the leaves turning yellow and brown. All trees, 

 without exception, were either infested or had been infested with IK 

 brevicomis, and every indication pointed to this species as primarily to 



a Huts. 48 and 53, Bur. Knt.. U.S. Dept. Agric. 



