When 18,416 adultScolytus multistriatuswere marked with a fluorescent powder and released, 27% were recaptured in pheromone-baited traps. Of these, 98% were captured on traps 1.5 m from the release point, but the maximum distance for capture was 160 m. In another phase of the study, adult beetles were marked with32P as they emerged from elm logs. Of 1964 beetles subsequently captured in pheromone-baited traps, 63% were 1.5 m from the emergence site. EndemicS. multistriatusfrom unknown sources were caught in all traps, with an avg of 2553/trap and a total of 51,059. They were found at all trap heights to 4.8 m.