This paper presents a study of three phases of the flight of the Douglas-fir beetle, viz: flight preparation and response, flight attitude and movements, and flight capacity. A room equipped with temperature and humidity controls was used for some of the experiments. The wing movements were studied with a stroboscope and flash photography. Flight mills were used in the studies involving flight duration and velocity. The only effect of nemic and mite associates was reduction of the duration of the initial flight caused by internal nematodes. Temperature played an important role in all phases of flight studied. Temperatures from 72° to 89° F. were optimum for spontaneous flight, while 68° F. seemed to be the lower limit of flight in the absence of additional stimuli. In sunlight, spontaneous flights occurred at 63° F. Increasing temperature caused a rapid increase in the wing-beat frequency up to the threshold for spontaneous flight, then increased only slightly to the level of heat prostration. Lower temperatures greatly reduced the duration of the initial flight and caused a broken flight pattern, but failed to influence the over-all flight duration. The effects of relative humidity followed a similar pattern to those of temperature inasmuch as evaporational cooling of the insect occurred at low relative humidities not at high relative humidities. Increased light intensity increased the speed of the flight response and caused slight increases in the wing-beat frequency; both results being attributed to increased nervous stimulation. Studies on the effect of the ehange in the beetles’ activity from dispersal to gallery construction to re-emergence, on the response to flight stimulation, showed that once gallery construction had begun the females became flight refractory, some regaining their inclination to fly after 15 days. On the other hand, the males could be expected to be either flight positive or refractory throughout the duration of gallery construction. The number of individuals responding positively to flight stimulation by tossing increased greatly following the first toss, then diminished until no further change occurred after six tosses. Wing mutilation and loading produced changes in the wing-beat frequency similar to those found by other workers, and indicated that the changes were probably due to altering the inertia of the oscillating system. Fatigue caused a gradual reduction in the wing-beat frequency over a four hour period although the final per cent decrease attributable to fatigue was much lower than that reported for other insects. The flight velocity was of the order of 90 to 115 metres per minute or 3.3 to 4.2 miles per hour, changes in the flight velocity seemingly being related directly to changes in wing-beat frequency. It is concluded from these studies that the Douglas-fir beetle is a strong uniform flier despite the complexity of components affecting several phases of flight. The various thresholds for spontaneous flight were consistently above the levels required for continuation of the activity. The flight of the Douglas-fir beetle can be expected to vary greatly from year to year and from season to season depending on the environmental factors. Of the flight movements it is the wing-beat frequency which is affected the most by environmental changes, thus varying the strength, velocity and magnitude of the flight. The Douglas-fir beetle is capable of an average flight of up to 10 miles immediately following take-off and from between 15 to 20 miles a day for several days; favourable air currents would increase these figures substantially. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--Oregon State University, 2004. / Typescript (photocopy). Includes bibliographical references (leaves 62-76). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2004. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 94-100). Also available on the World Wide Web.

Recent bark beetle outbreaks have caused extensive tree mortality in conifer forests across western Northern America, which has altered forest fuels. These changes have raised concerns about forest health and wildfire risk. Studies focused on interactions between bark beetles, forests fuels, and changes in fire behavior have been primarily led in upper elevation forests characterized by high-severity fire regimes, principally in lodgepole pine (pinus contorta Douglas ex Loudon) and Engelmann spruce (Picea engelmannii Parry ex Engelm) forests. Few studies to date have addressed bark beetle fuel interactions in lower to middle montane forest characterized by a mixed-severity fire regime, with available research focused strictly on assessing fuel load conditions or stand structural changes. The goal of this research was to quantify and characterize surface and canopy fuel changes in middle montane interior Douglas-Fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.)) forest infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins), while also measuring physical and chemical changes to foliage in terms of moisture content and terpenes, which are known to play important roles in foliage flammability. Our results revealed few changes in surface fuels following Douglas-fir beetle infestations aside from a significant increase in litter depth and loading in red stage sample plots. Substantial changes to canopy fuels were detected in the red stage of an outbreak with a significant reduction in foliar moisture content measured as tree crowns faded from a healthy green phase to red. During this period, volatile emissions and within-needle concentrations of terpenes increased, including some terpenes previously associated with increased foliage flammability in other tree species. Furthermore, aerial fuel parameters that estimate the likelihood of crown fire initiation, including canopy bulk density and canopy base height, showed a substantial reduction in gray stage sample plots. Based on our findings we judge the influence of Douglas-fir beetle activity on altering fuels is most pronounced in the aerial fuels complex. Our results suggest bark beetle affected interior Douglas-fir stands with a high percentage of trees in yellow and red crown phases could have an increased threshold for crown fire initiation based on higher levels of flammable monoterpenes and lower foliar moisture content.

Two study plots containing Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) newly infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) were established and photographed with large-scale (1:1000), colour infrared film on July 29. 1979 - approximately three months after possible insect attack. Ground checking confirmed attacked trees and also showed that at the time of photography all trees had visually green, healthy-appearing foliage. All trees, both attacked and non-attacked in each plot were matched to their photographic images, and visual photo interpretation for damage types and densitometric analysis of the original transparencies were done. For each tree-crown image included, the yellow, magenta and cyan dye layer density measurements were taken and these values plus three ratios derived from them were tested statistically using analysis of variance and stepwise discriminant analysis. Significant differences were found between the optical density values of the images of healthy and attacked trees. The ratio values had much smaller variances than did the individual dye layer densities and all three ratios showed significant differences between healthy and attacked trees. Stepwise discriminant analysis produced significant separation of damage classes. Two-thirds of the successfully attacked trees were correctly classified and were confirmed by a second ground check in January, 1980. It is concluded that successfully beetle-attacked trees have a unique spectral signature than can be detected on colour infrared air photos approximately three months after initial attack when the trees still support visually green, healthy-appearing foliage. / Forestry, Faculty of / Graduate