CHEMICAL COMMUNICATION IN HELIOTHINE MOTHS .6. PARALLEL PATHWAYS FOR INFORMATION-PROCESSING IN THE MACROGLOMERULAR COMPLEX OF THE MALE TOBACCO BUDWORM MOTH HELIOTHIS-VIRESCENS

The chemical and temporal features of the sex-pheromone emitted by Hel iothis virescens females are encoded by a diverse array of output path ways from the male-specific macroglomerular complex (MGC) in the anten nal lobe. Most output neurons (29 out of 32) were activated by antenna l stimulation with the principal component of the sex-pheromone blend of this species, (Z)-11-hexadecenal. Six neurons were excited solely b y this component, 8 neurons also responded to the second essential ble nd component, (Z)-9-tetradecenal, and 14 neurons displayed equivalent responses to the two. Many neurons also effectively encoded the onset and duration of the stimulus. In one additional neuron, a prolonged ex citatory response (synergism) was evoked only by the blend of the two components, indicating that some MGC neurons function as 'blend detect ors'. In contrast to the situation in Helicoverpa tea, none of the MGC neurons in H. virescens responded selectively to (Z)-9-tetradecenal, suggesting that these two noctuid species employ different neural stra tegies to encode information about their respective pheromone blends. Three MGC-output neurons responded selectively to (Z)-11-hexadecenyl a cetate, an odorant released by some sympatric species that disrupts no rmal upwind flight to pheromones. Thus, changes in the attractant and deterrent chemical signals, as well as the physical features of these odor plumes, are encoded in the MGC across a diverse parallel array of output pathways to the protocerebrum.