Mountain pine beetles from naturally infested lodgepole pine were marked with fluorescent powder in the laboratory, released in the field, and recaptured at lethal baited trap trees and in traps to study their temporal, vertical, and horizontal distributions and some effects of temperature and wind direction.Over 80 YO of the recaptured beetles were trapped within 3 days of release regardless of temperature and wind conditions; the proportion recaptured was directly related to heat accumulation above a flight threshold temperature of 16°C. Near the release point, the greatest numbers of marked beetles were trapped at a height of 3 m, and captures declined above and below this point. It was estimated that only 0.2 % of the marked beetles dispersed above the stand canopy. In a limited experiment, no naturally emerged beetles were captured above the stand canopy in traps suspended from a large balloon. Captures from the four cardinal directions decreased exponentially with distance from the release point. Most beetles were trapped upwind and downwind from the release point. A simple model based on the proportion of beetles trapped at a given (reference) distance from the release point was developed to estimate the proportion of released beetles which could be trapped at any distance.' Deceased.U.S.

An empirical method was developed for predicting the directional distribution of mountain pine beetles (Dendroctonus ponderosae Hopk.) responding to attractive semiochemicals. An emergence model relates relative hourly beetle emergence to mean hourly ambient temperature, a daily rhythm of emergence, and daily total number of emerged beetles. Trap catches were used as a relative measure of emergence. A dispersal model relates the relative directional distribution of dispersing beetles, searching for sources of attraction, to mean hourly wind direction and speed, and relative hourly abundance of dispersing beetles. The latter model includes a deflection angle relative to mean wind direction to allow for an assumed crosswind movement by searching beetles. Both models gave good fit to the experimental data, but wind speed had negligible effect on the fit of the model for relative directional distribution of beetles. When tested on independent data, the dispersal model gave good predictions of the numbers of self‐marked mountain pine beetles of three different colours trapped in passive traps at four trapping sites. This model also gave a reasonable prediction of the general directional distribution of attacked trees relative to the brood trees. More extensive testing is suggested to further explore the model structure and performance. Numbers of self‐marked mountain pine beetles trapped by time period, location, and height were also analysed and discussed in relation to flight behaviour of beetles. Zusammenfassung Über ein empirisch ermitteltes Modell zur Bestimmung des lokalen Dispersionsfluges von Dendroctonus ponderosae Hopk. (Col., Scolytidae) in Abhängigkeit von der Lockstoffquelle, der Windrichtung und der Windgeschwindigkeit Es wurde eine empirische Methode entwickelt, um die räumliche Verteilung von Borkenkäfern, Dendroctonus ponderosae, die auf Lockstoffe reagieren, vorherzusagen. Mittels einer Modellrechnung wurde die stündliche Ausschlüpfrate in Abhängigkeit von der mittleren stündlichen Temperatur, dem täglichen Schlüpfrhythmus und der täglichen Gesamtanzahl ausschlüpfender Käfer ermittelt. Als relative Meßgröße der Schlüpfrate wurden Fallenfänge verwendet. Durch ein Dispersionsmodell wurde in Abhängigkeit von der mittleren stündlichen Windrichtung und Windgeschwindigkeit die Dispersionsrichtung ausfliegender Käfer bestimmt, ebenso die relative stündliche Abundanz dispersierender Borkenkäfer. Im letzteren Modell wurde ein Abweichungswinkel berücksichtigt, um in Abhängigkeit zur Windrichtung einen Seitenwindeinfluß auf die Bewegung suchender Käfer auszugleichen. Beide Modelle paßten gut zu experimentell ermittelten Daten, jedoch hatte die Windgeschwindigkeit einen zu vernachlässigenden Einfluß auf die Anpassung des Modells an die relative Dispersionsrichtung von D. ponderosae. Mit dem Dispersionsmodell konnte eine gute Vorhersage erzielt werden, wie sich anhand von markierten Käfern in Fallen an vier verschiedenen Orten nachweisen ließ. Auch konnte mit diesem Modell eine begründete Aussage über di...

Bark beetles were trapped for two summers in a mature stand of lodgepole pine, Pinus contorta var. latifolia Engelmann (Pinaceae), infested by mountain pine beetle, Dendroctonus ponderosae Hopkins, near Princeton, British Columbia. Columns of flight-barrier traps were suspended next to uninfested live trees and from dead brood trees containing new adult beetles. The brood trees had been treated in the previous year with mountain pine beetle pheromone bait alone or in combination with Ips pini Say (Coleoptera: Scolytidae) pheromone bait and subsequently killed by mountain pine beetles. A total of 3376 individuals from 30 species of Scolytidae were captured in the traps. Most of the species for which lodgepole pine is a nonhost or occasional host were captured in low numbers (one or two specimens). The most abundant species (> 30 individuals) were D. ponderosae, I. pini, Hylurgops porosus LeConte, Pityogenes knechteli Swaine, and Trypodendron lineatum Olivier. The treatments affected captures of mountain pine beetles and I. pini but only in the year when trees were either unbaited or baited simultaneously for mountain pine beetle and I. pini. There were significant differences among the five most abundant species in the mean heights and mean Julian dates of capture. In addition to host condition requirements, these differences reflected partitioning of the food and habitat resource and competitive interactions among species. There was no interaction between treatment and trap height, indicating that treatment did not affect the height distribution of flying beetles.

Variation in bark beetle attack following spacing of mature lodgepole pine stands in the East Kootenays of British Columbia was analyzed in relation to stand location (site), spacing treatment, and harvesting injury. Observations were made on three sites, each having three treatments: 4 × 4 m spacing, 5 × 5 m spacing, and untreated control. There was no statistically significant difference in the numbers of attacked trees among sites or treatments. However, in the spaced plots 94.3% of the attacked trees sustained harvesting injury or were located adjacent to skid trails. Dendroctonus valens LeConte was the dominant species attacking trees on the two drier sites, and Dendroctonus murrayanae Hopkins was the dominant species on the third site. There was no statistically significant variation in the percentage of attacked stumps among sites or spacing treatments. On average, 80.7% of the stumps were attacked; attacked stumps had larger diameters than unattacked stumps. Thirteen species of bark beetles were found attacking stumps. Hylurgops porosus LeConte was the most numerous species at all three sites. Based on the fit of the Michaelis–Menten equations to species accumulation curves, an estimated 76–90% of the number of species attacking stumps at the three sites were observed in bark samples. Margalef’s index of diversity for the two drier sites (Cranbrook = 1.15, Parson = 1.13) was nearly identical and higher than at the moist site (Elkford = 0.89). Pairs of sites had five to six species in common, and the Sorensen coefficient of similarity ranged from 0.52 to 0.71, indicating moderate similarity in species composition. The abundance versus species rank relationship was fitted by three models: the MacArthur broken stick model, the geometric series, and the Zeta distribution. The latter gave good fit to data from two sites, but none of the fitted models gave satisfactory fit to data from the third site, mainly because of the high abundance of the second ranked species (Orthotomicus caelatus Eichhoff). Our results indicated that stand characteristics affected species assemblages and abundances of bark beetle species that attacked stumps. Management practices that minimize injury to trees during the spacing operations are emphasized to reduce attack by bark beetles.