Figure 4. — Radiographs of poor 

 quality result when moisture con- 

 tent of wood and hark is not uni- 

 form. Light streak represents 

 area of high moisture content, 

 the result of unequal distribu- 

 tion of bluestain fungi. 



The radiographic method does not appear to offer any clear-cut advantage over the 

 bark-removal method of sampling field populations of mountain pine beetles at this 

 time. Although estimates of live beetle numbers obtained by the two methods were 

 comparable, disadvantages of the radiographic method should be taken into account. 

 These are (1) costs of both time and material; (2) difficulty in detecting dead beetles 

 on radiographs and in assessing specific causes of mortality; and (3) lower emergence 

 of brood adults, but higher female survival rates in radiographed areas. 



Although these disadvantages of the radiographic method exist when sampling field 

 populations of mountain pine beetles, radiography could be a useful technique for study- 

 ing some aspects of bark beetle biology and behavior. In addition, radiography will 

 continue to be an important means for studying laboratory populations of bark beetles. 



10 



