at three attacks per 930 cm^ in all three phloem thick- 

 nesses (fig. 2). For example in phloem 1.5 mm thick, BP 

 was 19 for three attacks and only 24 for seven attacks; 

 for phloem 3.5 mm thick, BP was 63 for three attacks 

 and 71 for seven attacks. When estimating brood 

 production in wild populations, GD would be preferable 

 to AD because average GD declines with increased AD. 

 In addition, weather can greatly influence gallery length 

 per attack. 



The somewhat stronger association of brood produc- 

 tion to GD than PT in ponderosa suggests MPB 

 dynamics may be different than in lodgepole, where 

 brood production is strongly associated with PT 

 (Amman 1972a; Amman and Pace 1976). Average BP 

 per 930 cm^ in phloem 3.5 mm thick is 75 beetles in pon- 

 derosa pine in contrast to 112 in lodgepole. Differences 

 in continuity and intensity of infestations, which are 

 generally more severe in lodgepole, may be related to 

 these differences in brood production. 



NUMBER OF EGG GALLERY STARTS 

 PER 930 CM^ OF BARK 



Figure 2— Mountain pine beetle brood production per unit 

 area of ponderosa pine bark increases with both attack 

 density and phloem thickness. 



BP/930 cm2 = 0.9256 [Ul - ^ (7 - AD)" ] 



Ul = (1045.2083) (0.03937 PT)^-^ 

 = upper intercept 

 n = 2.78 + (18.3944) (0.03937 PT)^ ^ 

 where 



PT = phloem thickness in millimeters 



AD = attack density per 930 cm^ 



P < 0.01 



R2 = 0.38 



Limits: < AD < 7 



Beetle Size 



A multiple regression screen showed that female 

 length (FL) was related to the linear effects of PT and 

 GD. In this case, PT accounted for 22 percent (P < 0.01) 

 of the variance, and GD accounted for 11 percent 



(P < 0.05) of the variance in FL (table 3). The combined 

 model explained 35 percent (P < 0.001) of the veiriance 

 in FL. The seeded effects are shown in figure 3. 



Table 3— Multiple regression screen 

 for length of mountain pine 

 beetle females as a function 

 of ponderosa pine phloem 

 thickness (PT) and egg 

 gallery density (GD) 



Variables 



R2 



GD 



0.11 



GD2 



.09 



PT 



.22 



PT2 



.24 



GD X GD2 



.12 



GD X PT 



.35 



GD X PT2 



.36 



GD2 X PT 



.33 



GD2 X PT2 



.33 



PT X PT2 



.24 



GD X GD2 X PT 



.35 



GD X GD2 X PT2 



.36 



GD X PT X PT2 



.36 



GD2 X PT X PT2 



.35 



GD X GD2 X PT X PT2 



.36 



EGG GALLERY, M/930 Cm'oF BARK 



Figure 3— Female mountain pine beetle length declines as 

 egg gallery density increases, but beetle length increases 

 as phloem thickness increases. 



FL = 5.307 - 0.197 GD + 0.159 PT 

 where 



FL = female length in millimeters 



GD = gallery density in meters per 930 cm2 



PT = phloem thickness in millimeters 



P < 0.01 



R2 = 0.35 



Limits: 0.3 < GD < 2.1. 



5 



