the parasitoid trichogramma has been used worldwide as biological control agent due to its wide geographic distribution, high specialization and efficacy against many lepidopteran pests. biological and behavioral traits of trichogramma pretiosum riley parasitizing sitotroga cerealella (oliver) eggs were studied aiming to a better understanding of the results from parasitism and superparasitism. the variables investigated were: host acceptance and contact time by t. pretiosum on parasitized host, percentage of parasitoid emergence, number of deformed individuals produced, egg-adult period, sex ratio, offspring female body size and longevity, and number of s. cerealella eggs parasitized/female. parasitism rejection was observed on parasitized host eggs after 24, 72 and 120h of parasitism. the rejection was higher for eggs parasitized after 72h and 120h of parasitism as compared to the eggs after 24h of parasitism. t. pretiosum contact time on eggs after 24h of parasitism was greater than on 72 and 120h. the offspring produced from hosts from which a single parasitoid emerged were larger, exhibited no deformities and greater capacity of parasitism, different from those produced from eggs where two parasitoids emerged. offspring longevity, however, was similar for females emerged from hosts from which one or two adults emerged. in conclusion, t. pretiosum was able to recognize previously parasitized eggs and the superparasitism reduced the parasitoid.reproductive success.