INTRODUCTION 



Radiography as a tool to sample populations of the mountain pine beetle, 

 Dendroatonus ponderosae Hopkins, in lodgepole pine, Pinus aontorta Douglas, was tested 

 in the field. The objective was to determine whether radiography might prove to be a 

 better method of sampling mountain pine beetle populations than the bark-removal method 

 (Carlson and Cole 1965) currently used by this research work unit-^ to obtain life-table 

 data. 



Following a cohort of bark beetles through development would be more desirable than 

 obtaining sample estimates from different cohorts. Radiography makes possible such 

 study of cryptic forest insects, and has proved valuable in studying laboratory popula- 

 tions of bark beetles when frequent radiographs could be made (Berryman and Stark 1962a; 

 Johnson and Molatore 1961) . However, little field use has been made of radiography in 

 population studies of forest insects. 



Knight and Albertin (1966) used radiography in the field to study several insects, 

 including borers, Oberea schaumii LeConte and Saperda aonaoZor LeConte, in aspen, 

 Populus tremuloides Michx. , and the white pine weevil, Pissodes strobi (Peck), in 

 jack pine, Pinus banksiana Lamb. Radiography currently is employed by C. J. DeMars 

 (Entomologist, Pacific Southwest Forest and Range Experiment Station, Berkeley, Calif., 

 personal communication, July 27, 1973) to sample western pine beetle, Dendroatonus 

 breviaomis LeConte, populations. The western pine beetle spends much of its develop- 

 mental time in the outer bark of ponderosa pine, P. ponderosa Lawson. Infested bark 

 is removed from trees, taken to the laboratory, and radiographed. Time is saved and 

 accuracy is improved in counting forms on radiographs since the other method entails 

 dissection of thick bark to find insects for direct counting (DeMars 1963'), Similar 

 findings were reported for the southern pine beetle, D. frontalis Hopkins, when bark 

 samples from short leaf pine, P. e chinat a Miller , were radiographed (Fatzinger and 

 Dixon 1965). However, removal of bark for radiographing still represents a destructive 

 sampling technique and prevents workers from following a cohort through development. 



Unlike larvae of the western and southern pine beetles, mountain pine beetle larvae 

 in the thin bark of lodgepole pine feed and pupate primarily in the phloem layer against 

 the sapwood surface. Consequently, removal of bark samples for radiographing would also 

 expose larvae for direct counting. Therefore, any advantage of using the radiographic 

 method in the field would be in the accuracy and speed of sampling beetles in situ. 

 Radiographic sampling has been shown to give accurate counts of mountain pine beetles 

 in bark and wood slabs of lodgepole pine in the laboratory (Amman and Rasmussen 1969). 



Population dynamics of primary bark beetles. 



