THE WE8TERN PINE-DE8TBOYING BARKBEETLE. 



25 



It is probable that at higher elevations and farther north the 

 majority of the broods would not develop in much less than a year's 

 time and that at more south- 

 ern and warmer localities in the 

 Pacific Coast region there would 

 be two complete generations 

 and possibly a partial third. 



When first transformed, in 

 May and June, the young bee- 

 tles have very soft, delicate tis- 

 sues. They therefore remain 

 in their pupa cases until their 

 bodies are fully hardened or 

 chitinized. When nearly ready 

 to emerge, the adults bore their 

 way almost to the surface of 

 the bark (fig. 12, a), but pause 

 before emerging, appearing to 

 rest in the burrow, they have 

 just made. They do not, how- 

 ever, hollow out the space im- 

 mediately adjoining the pupa 

 case, as is the habit of another 

 species of this genus. When 

 quite ready to emerge, the bee- 

 tles continue their burrows out 

 through the remaining portion 

 of the bark. The individuals 

 of a brood do not appear to 

 emerge simultaneously, but 

 they come forth at irregular in- 

 tervals until all are out, leaving 

 the bark thickly punctured with 

 small, round, clean-cut holes, 

 as shown in figure 12. 



After leaving the tree or t in - 

 in which they went through 

 their transformations the bee- 

 tles fly away to find trees in 

 which to deposit eggs. They 

 may select trees close at hand 

 or may fly quite a longdistance before making a selection 

 also enter the living bark of recently felled trees. Larg< 

 61830°— Hull. 58—10 o 



. 11.— The western pine-destroying oarkbeetle 

 Dendroctontu brevicomis)'. Pitch tubes on bark of 

 i iriginal. | 



They will 

 numbers i f 



