The alfalfa seed chalcid,Bruchophagus roddi(Gussakovsky), is a host-specific insect that lays eggs in the developing seeds of alfalfa. In laboratory bioassay, females made in-flight evaluations of olfactory stimuli that emanated from an array of host and nonhost flowers. The outcome of choice tests depended on pretest conditions that varied in sequence and time of exposure to host and nonhost plants. Specific flight and landing behavior was elicited or inhibited by conditions that prevailed before the choice test. When females were confronted with a choice of different species of legume flowers (including alfalfa), they made more in-flight visits to the species to which they were exposed just prior to the test. Then, after in-flight evaluation of test flowers at close range, females made more landings on alfalfa. In addition, females made about the same number of direct landings on host and nonhost alike but without close-range evaluation of the flowers.