TEMPERATURE INDUCED VARIATION IN THE RATES OF REPRODUCTIVE PROCESSES IN DENDROCTONUS RUFIPENNIS (COLEOPTERA: SCOLYTIDAE): A NEW APPROACH TO DETECTING CHANGES IN POPULATION QUALITY

Abstract

To discover measurable parameters for detecting quality differences (with respect to reproduction) in insect populations, variations in temperature were utilized to obtain manifestation of quality at different levels. Rates of reproductive and associated processes such as yolk deposition, gallery excavation, and oviposition were measured in Dendroctonus rufipennis (Kirby) at four temperatures. Information presented here allows an estimation of D. rufipennis reproduction as affected by temperature. Among the various parameters measured the length of initial egg-free gallery and the number of eggs/unit productive gallery length and yolk deposition rate could be used to discriminate bark-beetle population quality. Rates of yolk deposition appeared most useful and widely applicable for this purpose.

COMPETITION AND POPULATION QUALITY IN DENDROCTONUS RUFIPENNIS (COLEOPTERA: SCOLYTIDAE)

“…Although the r-values were low owing to the high variability of the data, the trends found were those expected from the study of Sahota and Thomson (1979), with the exception of [3], which was not significantly different from a line of zero slope through the mean.…”

“…Sahota and Thomson (1979) indicate that, among different beetle populations, increase in population quality is FIGS. 1-2.…”

Forest Thinning Affects Reproduction in Pine Engravers (Coleoptera: Scolytidae) Breeding in Felled Lodgepole Pine Trees: Fig. 1.

“…In terms of temperature, our results are more consistent with laboratory studies that show increased reproductive rates with warmer temperatures. Females had longer galleries and laid more eggs at a higher egg density in thinned stands than in unthinned stands, just as seen in laboratory studies on the effects of increased temperature for other bark beetle species (Reid 1962, Amman 1972, Sahota and Thomson 1979, Wagner et al 1981, Wermelinger and Seifert 1999.…”

“…The distance to the Þrst egg in a gallery did not differ signiÞcantly between thinned and unthinned stands. Sahota and Thomson (1979) found that the distance to the Þrst egg decreased as temperature rises. Similarly, the distance to the Þrst egg is expected to decrease with fat content because energy reserves are available for immediate egg production upon arriving at a host.…”

“…First, reduced tree density and canopy closure make thinned stands warmer than unthinned stands (Bartos and Amman 1989;Schmid et al 1991Schmid et al , 1992aSchmid et al , 1992b; Bartos and Booth 1994;Hindmarch and Reid 2001). Controlled lab experiments have shown that as temperature increases, female bark beetles extend their egg galleries farther (Reid 1962, Sahota and Thomson 1979, Wagner et al 1981, lay more eggs (Wagner et al 1981, Wermelinger andSeifert 1999), have higher egg densities (Amman 1972, Wagner et al 1981, and lay their Þrst egg earlier (Sahota and Thomson 1979). However, in a Þeld study, Villa-Castillo and Wagner (1996) found that increased temperature due to thinning resulted in shorter egg galleries and lower egg densities.…”