The spatial distribution of attack around release sites in cotton fields was measured for the parasiteTrichogramma pretiosumRiley attacking eggs of the cabbage looper,Trichoplusia niHübner. The host eggs were presented 20/plant at equidistant “stations” in a cross pattern centered on the release site. Random diffusion theory predicts that the pattern should be a normal distribution in which the variance is a linearly increasing function of time. Out of 24 attack patterns, 14 were found to deviate significantly from a normal distribution. The deviations from normality tended toward a bimodal distribution. In addition, the time-trend of the variance showed a significant deviation from linearity. It is proposed that the deviations from normality may be due to time-varying drift and diffusion rates. In addition, saturation of the environment with parasites can cause a flattening of the attack pattern near the release site.