Recapture of dispersing bark beetle Ips typographus L. (Col., Scolytidae) in pheromone-baited traps: regression models

Parent (re-emerged) spruce bark beetles (Ips rypographus L., Col.; Scolytidae) beginning a second host-seeking flight were collected in pheromone-baited traps. These beetles were marked with fluorescent powder of different colors and released from a point source (9-16 June 1989) within a spruce, Picea abies L., forest (Jurbarkas forest district, Lithuania). Some of the marked beetles were recaptured with pheromone-baited traps in two experiments: (I) traps at 10 m and (2) traps 30, 60, 90, and 120m distances from the release point. Of 5920 and 5030 beetles that took flight in the two experiments, average recapture rates were 5.64 + 1.17% ( f SEM) on traps at 10 m distance, and 1.62 f0.2 I, 0.88 f 0.23, 0.27 f 0.08, and 0.03 f 0.03% on traps at the respective distances from 30 to 120 m. Parameters of several regression models were fitted with the Simplex algorithm (SYSTAT statistical software) to recapture data. The best fitting models were those of power, and an exponential form. A discussion ofthe biological meaning of certain coefficients in the equations is presented with regard to. bark beetle dispersal.