The effects of summer thinning on the population behavior of Ips avulsus (Eichh.) and Ips grandicollis (Eichh.) were investigated in a loblloly pine plantation in Tennessee. Thinning attracted large numbers of both Ips species, which infested slash in the experimental area. Beetles that invaded the thinning did not attack living trees; they only colonized fresh slash. Window-trap collections of flying beetles were significantly correlated with the intensity of attacks on slash. The flight of I. avulsus into each new thinning was briefer and more intense than the flight of I. grandicollis. Daytime temperatures and light also strongly influenced the flight intensity of I. avulsus. Newly emerged beetles, instead of accumulating in the old thinning, dispersed to new sources of attraction. Dispersal of I. avulsus was much more rapid than that of I. grandicollis. It is concluded that in pulpwood stands in the mid-South, Ips are rarely a hazard to healthy living trees because of summer thinning.