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 instance of medium-range migration by Rhopalosiphum maidis (Fitch) and of long-range migration by Spodoptera frugiperda (J. E. Smith) are documented and the weather systems that made the migrations possible are detailed. Although both species were carried beyond their northern limit for overwinter survival and little damage ensued, the usefulness of synoptic weather analysis in explaining sudden population increases is shown.

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...