none Cotesia melanoscela responds the same way to the silk of its host, gypsy moth larvae, Lymantria dispar L., whether or not it has previously been exposed to hosts. Parasites maintained in the laboratory for six or 25 generations also responded similarly, suggesting that orientation behavior is not modified by laboratory rearing. Details of silk-related orientation behavior were analyzed by tracing paths of female parasites when on or off silk-covered substrates. Females made 31 degree average turns every 0.5 cm whether or not they were examining silk. They tended to turn back onto a silked area when encountering a border, and their speed of movement when not examining silk was about three times higher than when examining silk.