none Rearing the parasitoid M. croceipes on hosts fed cowpea-seedling leaves instead of artificial diet increased the percentage of oriented flights to odors of a cowpea seedling-H. zea complex in a flight tunnel. However, the increase in response was much stronger after adult females had searched a fresh plant-host complex just prior to a test. The host plant appears to be of major importance in the parasitoid-host relationship: host-plant species, growth phase, and part of the host plant influence the parasitoid's response in the flight tunnel. Olfactory experience with odors of an attractive plant-host complex increased the response to an unattractive plant-host complex.