Factors Affecting Gallery Construction, Oviposition, and Reemergence of Dendroctonus frontalis1 in the Laboratory2

Abstract

The effects of constant temperature, adult density, female size, and month of adult emergence on gallery construction and oviposition per mating pair were examined for Dendroctonus frontalis Zimmermann. These factors interacted such that the effect of a single factor on reproduction could not be ascertained. Predictive models were developed to describe their combined effects on (1) total gallery and eggs per pair and (2) the cumulative proportion of gallery and eggs per pair through time. Models for (1) and (2) were consolidated to describe time-dependent reproduction per pair. Beetles constructed more gallery and laid more eggs at 15°C, whereas least gallery construction occurred at 30°C and fewest eggs at 10°C. Larger females emerging in February produced more gallery and eggs than did smaller females emerging in May or June. Total gallery and eggs per pair generally decreased with increasing pairs per dm2. Female size did not influence the timing of the cumulative distributions of gallery and eggs per pair, although temperature, density, and month of emergence did. The influence of temperature and density on daily fractional reproduction was described by a single empirical distribution function using constants to adjust the time scale. A separate function was needed to distinguish beetles emerging in February from those emerging in May and June. Weibull functions described the cumulative proportion of gallery per pair through time, whereas gamma functions provided similar descriptions for eggs. The effects of temperature, density, size, and month of emergence on the mean distances and times of initial and terminal egg-free and egg-bearing gallery were studied. The biological implications of these and other analyses on reemergence behavior were discussed.