10 



the technical or Latin name Dendroctonus ponderosa* The adult is a 

 stout, dark-brown to black beetle, individuals of which vary in length 

 from 4 to 7 mm. (about one-sixth to one-fourth inch). They attack 

 living and healthy large and small pine trees, enter the bark on the 

 main trunk, and each pair excavates a long, nearly straight, longitudi- 

 nal galleiy through the inner bark (PL I and fig. 1), usually grooving 

 the surface of the wood. Eggs are deposited along the sides of this 

 primary gallery and hatch into minute white grubs (larvae), which 

 excavate mines through the bark at right angles to the primary gallery 

 (fig. 1, Z>). These mines are extended and enlarged as the larvae 



increase in size, and when 

 full grown each individual 

 excavates a broad, oval 

 cavity in the bark (fig. 1, 

 <?), in which it transforms 

 to a soft, white pupa, and 

 then to the adult, which 

 bores out through the bark 

 (fig. 1, d), and flies, with 

 other adults of the same 

 and other broods, in search 

 of other living trees in 

 which to excavate galleries 

 and deposit eggs for an- 

 other brood. 



SECONDARY ENEMIES. 



Many other species of 

 bark beetles and other 

 bark and wood infesting 

 insects were found asso- 

 ciated with the primary 

 enemy in the partly living 

 bark of infested and dying 

 trees, but none of them were found making an independent attack on 

 living trees. Therefore they must be considered as secondary ene- 

 mies, which follow the leader in the attack, and merely contribute to 

 the rapid and certain death of the trees thus infested. 



The Oregon Tomicus (Tomicus oregoni Eichh.). This is a small red- 

 dish to black bark beetle, individuals of which vary in length from 

 3.5 mm. to 4 mm. It follows closely the attack of the pine-destroying 

 beetle, and enters the bark on the large and medium sized branches 

 and toward the top of the main stem. Several females excavate radi- 



a This species has heretofore been erroneously identified as D. terebrans and D. 

 rufipennis, and will probably be found so labeled in some collections. 



FIG. 2. Work of the Oregon Tomicus ( Tomicus oregoni Eichh. ) . 

 Primary galleries and larval mines in inner bark, ft, En- 

 trance; b, central chamber excavated through inner bark; 

 c, egg galleries; d, location of central chamber not exca- 

 vated through inner bark. Reduced about one-half (origi- 

 nal). 



